CERTAIN PHASE EQUILIBRIA

IN THE

SYSTEM TITANIUM-COBALT

Dissertation

Presented in Partial, fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State University

By

Prank Lewis Orrell, Jr., B.S., M.S. in Met. Eng.

The Ohio State University

1953

Approved hy;

Adviser Dedicated, to my wife,

Helen K. Orrell

A Q S 8 2 1 . iii

ACKN QWLBD&MEHT S

The author acknowledges the assistance of Professor

M.G-. Fontana, his adviser, in the prosecution of this investiga­

tion. He also wishes to express his appreciation to other members

of the Department of Metallurgy Faculty at The Ohio State Univer­

sity, Professors Deraorest, Lord, Speiser and Spretnak, for many helpfnl suggestions.

Gratitude is expressed to the follotting individuals and organizations for contributions which materially aided this program: Dr. S.F. Urban of the Titanium Alloy Manufacturing

Division of The National Lead Company for quantities of sponge

titanium and for the vacuum fusion analyses; Mr. J.B. Johnson

of the Wright Air Development Center for a generous supply of

iodide titanium; Mr* J. Kurtz of the Kulite Tungsten Company for a liberal quantity of cobalt metal; to Professor J.E. Shank of the Engineering Experiment Station of The Ohio State University and to the members of the Station's Analytical Division for the chemical analysis of many of the alleys studied; to Mr. P. Whibley of the Tube Laboratory at The Ohio State Univei*sity for construct­ ing the necessary apparatus and for sealing specimens in capsules.

Appreciation is freely expressed for the assistance of the persons, too numerous to list individually, who so willingly gave of their time for discussion or loaned equipment to aid this program. Special mention must be made of the innumerable kind­ nesses performed by Dr. F.H. Seek of The Engineering Experiment

Station and by the author's colleagues in the Department of Metal lurgy at The Ohio State University,

The author is grateful to The Titanium Alloy Division of The Mational Lead Company who sponsored the G-ra&uate fellow­ ship under which this work was conducted. V

TAB 15! OF COHTEETS Page

Introduction------1 Scope of the Investigation------2 Summary and Conclusions — ------3 Literature Survey ------5 Preparation of Alloys ------12 Choice of Technique ------12 Initial Arc Furnace Designs ------13 Final Arc Furnace Design ------1.6 Operation of the Furnace ------19 Melting Stock ------22 Homogenization and Equilibration — 23 Sealing ----- .23 Furnaces ------26 Heat Treat Schedules and Quenching------29 Examination and Analysis of Alloys ------32 Metallographic Technique ------32 X-Ray Diffraction ------3h Chemical Analysis ------35 Hardness Determinations ------.— 36 Resistivity Measurements ------3 6 Results and Discussion ------39 Preparation of Alloys ------r- 39 Homogenization and Equilibration------*------hi Determination of Beta/(alpha + Beta) Solvus ------h3 Determination of Beta/(Bets, -f-.TigCo) So l v u s ------h5 Determination of Beta-Ti2 Co Eutectic Temperature---■— h5 Determination of Ti2 Co—TiCo Peritectie Temperature --- h6 Verification of Eutectoid Decomposition — ------h6 Determination of the Crystal Structure of the Various Phases ------— ------h9 The Phase Diagram ------?------53 Hardness Determinations --- 5h Appendix ------5 6 Tables I — Chemical Analysis of Melting Stock ------57 II - Chemical Analysis of Alloys ------58 III - Microstructures of As-Cast Alloys ------59 IV - Micro structures of Homogenized Al l o y s ------60 V — Microstructures of Alloys Equilibrated for Beta/(Alpha + Beta) Solvus ------6 l VI — Microstructures of Specimens for Determina­ tion of Beta/Beta + Ti2 Co) S o l v u s ------— 62 VII - Determination of Beta-Ti2 Co Eutectic Hori­ zontal ------■----- 63 VIII - Determination of T±2Co -TiCo Peritectie Temp. 6h IX - X-Ray Diffraction Data for Specimen I8C163S--- 65 X - X-Ray Diffraction Data for Specimen 19 G1 6 3 1 7 0 D 66 vi TABLE OF CQHTEIJTS (Continued) Page Tables (Continued) XI - X-Ray Diffraction Data for TigCoCSpecimen I38C154A) ------67 XII - X-Ray Diffraction Data for Specimen I52C172A 68 XIII - X-Ray Diffraction Results for Specimen I68C177A 6^ XIV - Intorplanar Spacings of TICog from the L i t e r a t u r e ------70

Figures 1 . Arc Melting Furnace ------71 2. Schematic Diagram of Arc-Melting Furnace ------72 3. Accessories for Arc-Melting Furnace ------74 4. Arrangement of Apparatus for Sealing Specimens — 76 5. High Temperature Resistance Furnace .------77 6 . Circuit Diagram for High-Tenrperature Furnace 79 7. Equipment for Resistivity Measurements — 8 0 8 * Electrical Circuit for Resistivity Measurements - 82 9* Micro structure , As-Cast 2$Co A l l o y ------84 1 0 . Micro structure , As—Cast 5^Co Alloy -— --- 84 1 1 . Micro structure , As-Cast 9$Co A l l o y ------84 12. Micro structure, As-Cast 22^0 o A l l o y ------84 1 3 . Micros trueture , As-Cast Z6%Co A l l o y ------— 84 14*. Microstrueture, As-Cast 28^Co Alloy ------84 15• Microstructure, As—Cast 32$Co Alloy ------— 8 6 16. Micro structure, As—Cast 34^Co A l l o y ------8 6 1 7 . Micro structure, As-Cast 3 S$Go A l l o y ------8 6 18. Micro structure, As-Cast 3 8 $Co A l l o y ------8 6 19* Micro structure , As-Cast 46%C o A l l o y ------— 8 6 20. Micro structure „ As—Cast 5 2$ Co A l l o y ------8 6 2 1 . Microstructure, As-Cast 55/^Co Alloy ------8 8 2 2 . Microstructure, As—Cast 68^0o Alloy — *------8 8 23* Micro structure, Homogenized 2$&Go A l l o y ----- 90 24. Microstructure, Homogenized 5 t^Co Alloy — ------90 25* Micro structure, Homogenized 9^Co A l l o y ------90 2 6 . Microstructure, Homogenized l8 ^Go Alloy — ------90 27* Microstructure, Homogenized 24$Co Alloy ------90 28. Microstructure, Homogenized 2 6 $Go A l l o y ------90 29. Micro structure, Homogenized 2 8 $Co A l l o y ------92 30. Microstructure, Homogenized 30^Co Alloy ------92 31* Micro structure, Homogenized 32$Co Al l o y ------92 32. Microstructure, Homogenized 38$Co Alloy ------92 33. Microstructure, Homogenized 46$Co Alloy ------9 2 34. Microstructure, Homogenized 55^0o Alloy ---- 92 35* Micro structure, Homogenized 6Q%Co A l l o y ------94 3 6 . Microstructure, 6%Co Alloy Equilibrated 3 6 0 hours at 7 C0 °G. 9 6 37* Microstructure, 8$Co Alloy Equilibrated 360 hours at 700°C. ------96 vii TABLE OF CONTENTS (Continued)

Figures (Continued) 38. Micro structure , 12^Co Alloy Equilibrated 360 hours at 700°C. — ------— ------96 39* Microstructure, 8^Co Alloy Equilibrated 510 hours at 650°C. ------98 40. M icr os true ture, 9$Co Alloy Equilibrated 2l6 hours at 675°C. 98 4-1. Mi cros true ture , 9^Co Alloy Equilibrated 216 hours at 675°C . 98 *f2. Micro structure, l8^Co Alloy Heated Above Eutectic Temperature ------100 if3 . Microstructure, if6j&Co Alloy Heated Above Beritectic Temperature ------100 4A. Microstrueture 8$Co Alloy Equiliterated 56if hours at 675°C. 102 if-5* Mi cros true ture, 9^Co Alloy Equiliterated 216 hours at 700°C. 102 if6. Microstrueture, lO^Co Alloy Equiliterated 56if hours at 675°C - 102 4-7* Ti—Co Equiliterium Diagram ------103 48. Comparison of the Effectiveness of Various Solute Elements on the Lowering of the Beta—to—Alpha Transformation Temperature of Titanium ------— ----- *------104 49* Hardness vs. Composition for Binary Ti-Co A l l o y s ------105

Literature Cited ------106 Autobiography ------112 1 GKRTAIU PHASE aQUIUIBBA IK THE SYSTEM

TITAETUM - COBALT

Introd.Ti.ct ion

The advent of commercial production of titanium metal in

1 9 ^S was accompanied by the most optimistic predictions as to its future place among engineering materials. Such appellations as

"wonder metal", "miracle metal" and "Cinderella metal" were un— blushingly applied. Since that time, as would be expected, the superficial exh.uberan.ee has abated but the intensity of effort de­ voted to metal and alloy development has continued undiminished. .

The situation with regard to the development of titanium is also unique in that there has been a concomitant, although not equal, effort devoted to the study of titanium equilibrium systems. Know­ ledge of the various phase equilibria is a prerequisite for the rapid and efficient development of alloys and for wise engineering application and economical industrial use of these alloys.

Although investigations of titanium equilibrium systems are being conducted in a great many laboratories, this total program is only a small part of the research needed to develop and establish the technology of titanium. The selection of cobalt as the second element was based on two considerations: first, the importance of cobalt as a base for high-strength, high temperature alloys was well (6 7) * established; second, there was no indication that study of the

* The figures in parentheses pertain to references which are listed in the Appendix. 2

titanium-cobalt system was being included in the initial phase of

the work on titanium. ( 6 8 )

Scone of the Investigation

The aim of this investigation was to determine as much

as possible of the phase diagram, concentrating on the solid phase

equilibria and \-irorking from the high-titanium end toward 1 0 0 ^> cobalt.

The principal endeavor throughout the program was always directed

toward avoiding or minimizing gaseous contamination. Although all

commercial titanium alloys contain small amounts of carbon, oxygen and nitrogen as impurities, these small additions markedly increase (69 70 the hardness and strength of titanium *' ) and alter the phase equilibria. Oxygen contamination, for example, of alloys in a binary system will produce a pseudo-binary system or, more correctly a ternary system.However, the obvious starting point for con­

struction and interpretation of ternary equilibrium systems is com­ plete knowledge of the component binary systems. Consequently, the design and construction of the special equipment necessary for this work and the development of satisfactory techniques constituted a considerable portion of the program. 3 SUMMARY AND CONCLUSIONS

1. A diagram was constructed showing phase equilibria in the sys­

tem titanium cobalt from one to fifty-five percent cobalt (see

Figure ^7).

2. The maximum solubility of cobalt in the high-temperature modifi­

cation of titanium (body-centered cubic; beta phase) was found

to be approximately 1 ?$ cobalt at 1 0 2 0 + 5 °C.

3 . The solubility limit of cobalt in the beta phase was found to

decrease from a maximum of 1.7% 3-t 1020+ 5°C. to a minimum of

approximately 10^ at 7 0 0 °C. in a curvelinear fashion.

The lowering of the beta-alpha transformation temperature by

addition of cobalt was found to be an almost linear function of

cobalt content. The lowering effectiveness of cobalt determined

in this investigation agreed closely with that reported by

McQuillan

5* ‘The location of the eutectoid point was indicated as being

approximately 9 •5% cobalt and 685± 1 0 °C. by the intersection of

the beta/(alpha + beta) solvus and the beta/(beta + TigCo)

solubility curve.

6 . The eutectic composition was estimated to be approximately Z7%

cobalt and the eutectic reaction isotherm between beta phase

and TigCo to lie at 1 0 2 0 + 5 °^.

7. The compound TigCo was found to be formed by peritectie reaction

between liquid and TiCo at 1055± 5°C.

8 . The presence of three intermetallic compounds in the system was confirmed (TigCJo, TiGo and TiCo2 ) •

9- The structure of TigCo was in agreement with, that reported by 7 o Wallbaum and by Duwez ^°h* ao =. 1 1 * 3 -A-) which according to Hostokrer and Earlson is the structure for Tij^CogO) .

1 0 . The structure of TiCo agreed itfith that previously reported:

Gs C l , a 0 — 3-00 A.

An alloy of the exact composition of the third compound TiCo2 »

was hot obtained. The structure obtained for this compound

agreed with that reported by Wallbaum (face—centered cubic)

bat not that reported by Duwez (hexagonal).

11. Suitable equipment for the arc melting, heat treating and exami­

nation of binary titanium-cobalt alloys was constructed. Satis­

factory techniques for performing these operations were a con­

comitant development.

12. Alloys o±* 1 to 6Q% cobalt were prepared by arc—melting and were

examined chemically, metallographically, by hardness testing

and by x—ray diffraction in a variety of heat treated conditions

to determine the phase equilibria. 5

LITERATURE SURVEY

It would appear from a thorough search of the literature that there has never been a comprehensive study of the binary sys­ tem titanium-cobalt. Earlier investigators of the system seem to have had as an objective only the acquisition of information con­ cerning the crystallography and stoichiometry of intermetallic compounds, particularly those formed by transition elements. Cer­ tain other investigators of about the same period, being interested in the role of cobalt in magnetic materials, were concerned only with the effects of titanium (and other elements) on the curie point and allotropic transformation temperature of cobalt.

In the search for new improved engineering materials among titanium-base alloys, some attention has been directed to the titanium-cobalt system. Among those writing on the trends in titanium alloy development, Gf-onser^^^ and Rostoker and Kessler have predicted that the system titanium-cobalt would be similar to the Ti-3Pe and Ti-Ni systems in that it would display decomposition of the terminal high-temperature phase in a eutectoid reaction.

la 1937 Kroll reported in a study of deformable titanium (if-8 ) • alloys that alloys of 2—9$ cobalt were readily hot worked. He stated that these alloys showed .a second phase and that the 5 $ cobalt alloy had a melting point of 1500°C.

In 19^9 Larsen, et a l , ^ ^ prepared a sintered and x*olled alloy having 10$ cobalt. They report that this alloy melted at 1 2 0 0 °C. blistered at 1125pC. and homogenized satisfactorily at 925°C. They were able to cold roll the heat treated alloy to a

1 5?° reduction in thickness but further reductions were not possible even after annealing treatments.

In 1950 Craighead, Simmons and Eastwood^^ published their results of a comprehensive survey of binary titanium—base alloys containing various alloying elements in amounts up to 10% by weight.

Cobalt alloys made from Kroll process titanium sponge and up to

3% cobalt were studied. In general, they found that additions of cobalt produced some increase in strength with a considerable loss in ductility. In particular, they propose that cobalt additions lower the temperature of the titanium allotropic transformation.

They indicate a solubility of about 1.5^ cobalt in alpha (low- temperature, hexagonal close-packed modification) titanium at 7 8 8 °C.

At 84’3°C. alloys of one, two and three percent cobalt showed a two- phase structure, alpha plus beta (high-temperature, body-centered- cubic modification of titanium).

McQuillan has recently made an extensive study of the alpha-beta transformation in titanium reporting on the temperature of the transf ormation, (5 1 *5 2 .) Qn titanium-hydrogen system, on the effects of Impurities in magnesram-reduced titanium on the alpha- beta transformations in the titanium-hydrogen system,^^'^^ and on the effects of the elements from vanadium through copper in the periodic table on the alpha-beta transformation.(-^»55)

McQuillan's method consisted essentially of heating a sample at a high temperature in an atmosphere of hydrogen until equilibrium between dissolved hydrogen and the atmosphere was

attained. The temperature of the sample was lowered, equilibrium

established at the new temperature and the hydrogen pressure in

the system determined. This procedure was repeated several times

and from the data obtained the logarithm of the pressure was

plotted against the reciprocal of the corresponding absolute temp­

erature for each composition studied. Since each phase has a

characteristic maximum solubility for hydrogen at the same temper­

ature and since at equilibrium the dissolved hydrogen is parti­

tioned among the phases present, there is an abrupt change in the

log p vs. ■*"/T curves at temperatures at which phases transform or

at which the number of phases increases or decreases.

Of the many results reported by McQuillan those which are most immediately pertinent to the subject of this investigation are the following:

a. cobalt is almost completely insoluble in alpha—

titanium

b. there is extensive solubility of cobalt in beta—

titanium

c. the beta—to—alpha transformation is not suppressed by quenching from high temperature for compositions below five atomic-percent cobalt

d. the eutectoid decomposition of alpha—plus—beta to alpha-plus-gamma (or beta to alpha—plus—gamma) is hot observed for compositions below five atomic—percent cobalt e. the addition of cohalt to titanium lowers the beta

to alpha-plus-beta transformation temperature in an almost straight-

line fasion from 882°C. for pure titanium to 725°G* for titanium plus five atomic-percent cobalt.

The high-cobalt end of the diagram has been studied by

Hashimoto^^ who reported that additions of titanium and of zir­ conium raise the allotropic transformation temperature of cobalt.

Hansen^^ records some work of Egeberge in 1915 with very impure alloys containing up to 10.9^ titanium. He concluded that a cobalt

solid solution containing about 3 »5^ titanium formed a eutectic at

18 — 2.0°/o titanium with a phase of unknown composition.

From a study of the effect of certain elements on the magnetic and polymorphic transformations in cobalt Koster and

Magner^®^ concluded that the maximum solubility of titanium in cobalt at 8 9 0 °C. was 7 -2^> and that additions of titanium lowered the polymorphic transformation temperature of cobalt*

The intermediate phases in the titanium-cobalt system have received the greatest amount of previous attention. During a study of the ternary system iron-cobalt-titanium in the range

0-22/S titanium Koster^^^ reportedly found only compounds having the stoichiometric ratio Fe^Ti and C03T 1 which were mutually soluble.

From. 1939 to 19^1 Wallbaum published three papers dealing with the crystal structure of titanium-cobalt intermetallic compounds and the phase relations among those compounds.(6 0 ,6 1 ,6 2 ) rp^e results of those investigations can be summarized as follows: 9

a. There is a eutectic between titanium (Y/allbaum

does not mention solid solubility limits) and TigCo occurring

at about 2.5CJ> Cobalt and 1590°C.

b. The compound Ti2Co melts congruently at 1 6 0 0 °C.

and has a face—centered cubic crystal structure with 9 6 atoms

per unit cell.

c. The compound TiCo is formed by peritectie reaction

at 1450°C. It has a body—centered cubic structure of the CsCl

type.

d. The compound TiCo2 is formed by peritectie reaction

at 1250°C. It exists In two forms, one, stable at high tempera­

tures and over a narrow range of composition at room temperature

with an excess of titanium; the other, stable over a wider range

of composition when cobalt is in excess. The high-temperature

form has a face-centered cubic structure of the MgCu2 (C15) type . o, with 24 atoms per unit cell (aQ = 6.69A). The cobalt—rich form

has a hexagonal structure of the MglTi2 (C3 6 ) type with 24 atoms

per unit cell (a = 4.7-^i c = 15«*4A; c/a = 3 *2 6 ).

e. There is a eutectic between TiCo2 and Co at 8 l^»

cobalt and 1 1 3 5 °C.

In 1950 Duwez and Taylor^^) reported on the results

of their study of the crystal structures of intermediate phases

in alloys of titanium with iron, cobalt and nickel. They confirmed

Wallbaum’s structure for the phase Ti2Co and measured the unit

cell size (ac = 11.283kX). They also confirmed the presence and • . 10

structure of TiCo giving its parameter as aQ = 2.988kX. However,

they found no evidence for the existence of. Wallbaum1 s TiCo2 cubic structure hut did confirm the hexagonal TiCo2 phase for alloys having compositions on either side of the exact stoichio­ metric ratio for TiCo2 -

More recently the previously reported structures of the TigX phases have teen questioned. While studying the titan— ( 64) ium—copper system Karlsson encountered contEunination of the alloys as a result of reaction Detween the metal and the glass capsule in which the samples were sealed for heat treatment. He reports finding among phases containing a variety of combinations of titanium, copper, silicon and oxygen a titanium— copper-oxygen o phase with a face-centered cubic structure (aQ = 11.24 — 11.44A) .

He proposed that this phase was the same as that reported by Laves and Wallbaum^0^ as Ti2 Cu with 96 atoms per unit cell. He extended this work to a study of a number of metal—titanium—oxygen systems^-5) and found oxide phases of the type Me3 Ti3 0 , where Me — Mn, 3Pe* Co,

Hi and Cu but not V", Cr, or Zn. He proposed that the Me^Ti^O phases were isomorphous with the Fe^W-^C phase in high-speed steels. He further suggested that the phases Ti2 Mn, TigFe, Ti2 Co and Ti^Hi as reported by laves and Wallbaum were probably identical with the corresponding Me^Ti^O phase.

In 1952 Hostoker^^ reported results of a more thorough examination of the Ti2^ problem. In general his results agree with those of Earlsson, indicating a, family of compounds isomorphous with G with compositions ranging from TifyX^O to Ti-^X^O.

When X is Cu or IsTi this structure occurs with or without oxygen.

If X is Co, 3?e or Mn, the structure occurs with oxygen, "but not without. If X is Cr or V, the structure does not occur under any conditions. Of particular interest are his findings that

Ti2j.Co20 has a face-centered cubic structure (Fe^W-jC type; a c = 11.295 h and TigCo is "predominantly cubic, MgCu£ type, aQ = 6.73-a-“, similar to Wallbaum'a structure for TiCo2 * ^ ^ PREPARATION OP ALLOYS

Choice of Technique

There are, in general, three techniques which hare been most widely used in the prepara/bion of titanium—base alloys:

a* pressing and sintering of metal powders;

b. melting in a refractory crucible;

c, arc melting in a consumable or non-consumable

electrode furnace.

The first method has been used by long et al^*^ in a preliminary

investigation of the titanium-nickel system and by a number of other investigators, such as Cross^^’ Jaffee^-^ and Kuhn.^^, in a screen­ ing of titanium-base alloys. While this method does, perhaps, pro­ vide certain advantages it is generally conceded that appreciable a- mounts of oxygen and nitrogen are introduced with the powders.

The use of refractory crucibles has been studied by (O McPherson and Fontana-' during their investigation of titanium- chromium alloys and by Brace et al^' during their general survey of titanium-base alloys. None of the refractories tested appeared capable of consistently yielding melts free of contamination. Al­ though melting in a graphite crucible is the method for commercial ingot produc tion^^, a "pick-up" of 0 - 1 .5 $ C is experienced^^.

Perhaps the most widely adopted laboratory method for successful melting of reactive and refractory metals involves use of the electric arc. It is interesting to note that one Robert Hare in (9) 1839 melted platinum in an arc furnace which, according to Kuhn , 13

contained many of the "basic features common to. those currently' used

for melting titanium. In 1905 t o n Bolten^"*"^ melted tantalum against

a water-cooled copper surface using a consumable electrode. R.W.

Moore used a similar process in 1923 for melting uranima^1^. More

recently the same features were. employed by Parke and Haia^^^ for melting molybdenum under vacuum using consumable electrodes and a water-cooled copper mold. Kroll^-^ modified the von Bolten furnace by replacing the consumable electrode with tungsten. Finally, the von Bolten-Kroll furnace was adeopte by Siimnons^ and by Herres and DaTis^1 ^ for titanium with satisfactory effectiveness in melting and freedom from contamination*

Initial Arc Furnace Designs

In selecting a method for preparing the alloys for this work the desire to have such alloys as free as possible from gaseous and other contamination precluded the use of powder metallurgy and refractory crucible melting. Since the melting points of titanium and cobalt are not too widely separated there was no need to consider using the consumable-electrode method (also the consumable electrodes are prepared from powders). There was available in the Department an arc-melting furnace with a tungsten—tipped electrode which had Cl1} 7 9 ) previously been used in a study of titanium-chromium alloys .

This apparatus was re-assembled and a number of unsuccessful attempts were made to prepare 1 0 to 15 gram melts. The chief difficulties with the furnace appeared to be as follows: . a>

a. the system was far from vacuum-tight making it impos­ sible to purge it of air and permitting back—diffusion of oxygen and nitrogen;

b. the capacity of the furnace (2 -l/2 pounds) was so large that it was exceedingly difficult to melt 1 0 -gram buttons without frequently burning through the copper crucible;

c. the cons tract ion of the furnace was such that, while quite satisfactory for the work for which it was designed, it made the use of the furnace for very small melts very clumsy and ineffi­ cient. (it was difficult to see and follow the action of the arc.

The furnace had to be opened after each melting to turn the button over, then closed and re-flushed - an operation consuming considerable time). After a study of the foregoing it was felt that there were only two alternatives, one, to rework completely the existing equip­ ment or, two, to construct a new furnace whose design would provide more efficient operation than could be obtained even by reworking the old furnace. The advantages of fast and easy melting appeared so attractive that the latter course of action was elected. Accordingly a new furnace was designed and constructed.

This new furnace consisted essentially of a pyrex glass cylinder six inches in diameter by eight inches long closed at the top and bottom by brass cover plates. The brass plates were water cooled by means of l/8 M diameter copper tubing soldered to the plates. The

Joints between the brass plates and the glass cylinder were originally sealed by flat rubber gaskets. Vacuum and gas connections. were made ■15 through suitable openings in the base.plate. The top plate contained an access cover sealed by an O-ring which could be quickly and easily removed and replaced without disassembling the furnace. The tungsten- tipped electrode entered the furnace through the access cover. Also included in the access cover was a long rod whose manipulation would permit turning melted buttons over without opening or otherwise dis­ turbing the furnace. Motion of the electrode and turn-over rod was obtained while maintaining a vacuum seal by means of Sylphon bellows attached to the electrode and rod and to the access plate by suitable fittings. The melting hearth consisted of a copper’ block four inches in diameter by four inches long. Into the top surface of the block were machined four cavities to permit melting four different alloys in the one furnace operation.

After the apparatus described above was machined it was assembled and a large number of melts were prepared. Most of the desired features with regard to speed and ease of operation were real­ ised but buttons free of gaseous contamination could not be consistently obtained. Considerable work with the furnace led to the conclusion that the chief source of difficulty lay in the seals between glass cylinder and the brass cover plates, A variety of remedies (including glyptal and a number of vacuum waxes and greases) were tested to find a reliable seal. When these efforts failed the furnace was disassembled and reworked to change the seals from flat gaskets to O-rings. While the use of an O-ring seal improved the performance of the furnace it did not bring it to the desired level so the problem of providing a.6

suitable means for preparing tlie alloys was re-evaluated . It was decided that making the glass-walled furnace vacuum tight would

require certain materials whose availability to this program was

questionable and, in particular, machine work requiring a degree

of skill the writer did not possess* Accordingly, it was elected

to abandon the new furnace and to rework the older furnace*

Final Arc Furnace Design

Complete details of the arc melting furnace as formerly used for the preparation of l/*f — to — 2 — 1 /2 —pound ingots are given by McPherson^^^ . The furnace and accessories as modified for use in this investigation are shown in Figure 1 . The arrangement of

the auxiliary components is best seen in the schematic diagram shown in Figure 2 . Certain parts of the furnace are shown in greater detail in .Figure 3* The alterations to the older furnace made during modification were as follows:

1 . The furnace charging device was removed at the seal below the funnel. Since the tubular feed arm could not be removed without extensive repairs to the furnace top, the seal was modified to permit use of an O—ring and the joint capped. The feed arm was bent to a greater angle to permit more lateral movement of the electrode.

2 * The existing electrode was discarded and a new one constructed to permit use of l/ 2 —inch diameter tungsten rod for the tip in place of the former 3 l &—inch tip to give better control of the arc. Instead of brazing the tungsten tip directly to the 17 electrode a copper plug- was made and silver-soldered to the electrode.

Into the exposed end of the plug a 5/8” - 14 female thread was ma­

chined. Over one end of the tungsten rod (about two inches long) a copper ring about l/2-inch long was shrunk-fit and then silver-solder­ ed to the tungsten. This copper ring was then machined and threaded to fit the copper plug. The opposite end of the tungsten rod was ground to a hemispherical shape to complete the electrode tip (see jS’igure 3 ). This alteration provided three important advantages: one, since copper is much easier to braze or solder than tungsten, a more perfit joint wa.s assured than in the case of brazing the tungsten tip directly to the electrode; two, at the point where water leakage into the furnace could occur if a joint failed even slightly through over-heating, the thermal resistance of the brazed joint was improved by making it copper—to-copper; three, the tungsten tip could be cleaned quickly and easily simply by unscrewing it from the electrode, thus eliminating the time-consuming task of removing the entire electrode from the furnace and the awkward and ungainly manipulation of the electrode while grinding the tip.

3- The stainless steel bellows and G-ooch tubing device formerly used to provide a flexible seal between electrode and furnace was discarded. It was replaced by a Sylphon seamless copper bellows which was soft-soldered top and bottom to suitable fittings. The top fitting contained a groove for an 0—ring and was fastened by cap screws to an annular-ring cap. The cap was in turn soft-soldered to the electrode. The bottom fitting was screwed into the top of 18

the furnace and the joint sealed "by means of an 0 —ring placed under

a shoulder on the fitting. As far as vacuum tightness in the system was concerned this was probably the most important modification made for the original bellows contained a longitudinal seam closed by a mechanical joint and the Gooch tubing is too porous for vacuum applications of this type.

*}-. To provide a suitable hearth for making the small melts required in this program, a copper block about 2 -1 /2 -inches in diameter by l-l/2-inches 3„ong was machined to fit snugly into the bottom of one of the flat-bottom copper crucibles used in the previous work. Into the top of this insert were machined two cavi­ ties, one, 5 /8 —inch diameter by l/2 -inch deep and, the other, one- inch diameter by l/2—inch deep. A short piece of tungsten rod was inserted in the top of the block to serve as an igniter for the arc.

The complete insert and one of the copper crucibles can be seen in

Figure

5. Several other relatively minor changes were made such as correcting the size and shape of the 0 —ring grooves in the insu­ lating ring, shortening vacuum lines, eliminating unnecessary stop cocks and lines, adding a McLeod gage, all of which improved either the tightness of the system or the usefulness of the furnace. Operation of the Furnace

In general, three sizes of melts were prepared, three-

grams, five-grams and ten-grams, each requiring a slightly differ­

ent melting technique from the other. The details of each step in

the operation of the arc melting furnace for preparing these melts

are given below.

1 . Suitable pieces were cut from the iodide crystal bar

and the cobalt slabs and weighed to one-tenth milligram on an anal­ ytical balance. Except in the case of alloys with very small cobalt content no attempt was made to adjust the amount of either constituen

closer than about 20 milligrams to the amount calculated for the

size of the melt involved.

2 . The weighed charge was placed in the clean copper insert taking care to arrange the smallest particles In between the largest pieces in such manner that the smallest particles would not be scattered by the arc nor so separated from the bulk of the charge that they could not be ''melted in."

3. The insert and charge were carefully positioned on the bottom of the spun crucible, the insulating ring and top placed in position and the furnace closed by tightening uniformly the four clamps.

h. The vacuum pump was started, the vacuum-line stopcock opened and hot water caused to flow through all parts of the furnace.

After about 1 /2-hour the pressure in the system was checked with the

McLeod gage. If the pressure were between 1-10 microns the vacuum 20 stopcock: was closed and the system filled with helium to a pressure slightly above atmospheric. The system was then pumped out and the flushing operation repeated about six times. After the final flush­ ing the hot water was replaced by cold and the system refilled with helium (Bureau of Mines, Grade A) to a slight positive static pres­ sure.

5- The electrode was lowered and the arc struck "between the tip and the igniter button. The arc was transferred then to the charge by executing a quick sweeping motion with the electrode. The arc was played on the charge for about one—half minute describing a circular motion with the electrode to promote thorough melting and mixing. Melting currents from 125 to 175 amperes were used, the choice depending on size of button and alloy characteristics.

6 . When the melting operation was finished and before opening the furnace the cooling water was replaced by hot water which was allowed to circulate until the temperature of all parts of the furnace equaled that of the hot water. Upon opening the furnace the copper insert was quickly removed and the inside of the furnace wiped clean as rapidly as possible. The insert was carefully cleaned and the tungsten electrode tip ground to remove all titanium, copper or cobalt deposited thereon. The furnace was then reassembled and the evacuating, flushing, heating and cooling cycles described in the foregoing were repeated.

7* The essential differences in technique for the prepara­ tion of the three sizes of melts were as follows. In the case of 21

three-gram melts, the molten button was allowed to cool /anti! color­

less then the arc was struck and the "button remelted without having

opened or otherwise disturbed the furnace. When the "button h«d

been melted four times the furnace was opened and cleaned as de­

scribed above, the button turned over on its back and again melted

four times as just described.

The five-gram melts were melted just once then the

furnace opened and cleaned as above. The button was then turned

over and remelted. After the second melting the button was

removed, set up on edge and melted. For the fourth and final melt­

ing the button was again edge—melted.

The ten-gram buttons were melted, turned and remelted

as above. The button was then cut through the middle. Cutting

the buttons proved to be something of a problem because of the

considerable hardness of the majority of the alloys. After a

number of methods had been tried a means was evolved which was

successful albeit a time-consuming nuisance. A simple fixture was

constructed similar to that shown in Figure 3 which was used for

cutting thin, parallel-faced slabs or strips from the buttons. When

the button was correctly positioned in the fixture with respect

to the slot, the ring was filled with Wood*s metal thereby locking

the button in position. A cut was then made along the slot using a Buehler abrasive cut-off. A water-cooled l/32-inch wheel was used to minimize loss of alloy in the saw kerf. The fixture was immersed in boiling water to free the pieces from the low-melting 22

alloy. The two halves of the button were then placed in the

crucible insert with one cut face up and one down and melted.

The button was then turned and melted for the fourth time.

Melting Stock:

In the earliest exploratory stages of the program a

number of melts were made using titanium sponge which was supplied

by the titanium alloy Division of the National Lead Company. How­

ever, all alloys used in the investigation were prepared from

iodide-process titanium (lots #IT-98 and #IT-1040 manufactured by

The New Jersey Zinc Company and made available to this project by

The Wright Air Development Command, Wright-Patterson Air 3?orce

Base, Ohio. The cobalt used for the alloys, although not as pure

as the titanium was the best available at the time in solid form.

It was supplied by The Kulite Tungsten Company of Union City, New

Jersey. Chemical analyses of these materials are shown in Table I

in the Appendix. 23

HOMQG-EHIZATIOR AMD EQ.UILIBRATIOH

Sealing

Since titanium and most titanium alloys readily absorb

oxygen and nitrogen* particularly above the alpha—to-bet a trans­

formation temperatures, (16,17,18) an^ since s u c h absorption has a pronounced effect upon the various gas—free equilibria, (19,20,21)

it is necessary to protect these alloys from the atmosphere during heating if contamination effects are to be minimized or avoided. 5’or heat treating at very high temperatures (above 1000°G to 1200°C) a common practice has been to place the specimens in some type of furnace provided with a closed furnace tube in which could be 22 maintained a purified inert atmosphere. ( ) Some investigators have added the extra precaution of surrounding the samples with titanium turnings and a titanium sleeve.^^ Another method which has seen at least limited use at Ann our Research IPoundation^^ consists of placing the specimens in a thick-walled, titanium con­ tainer which has been evacuated and then filled with an inert atmosphere and sealed. The method which has been universally used at lower temperatures involves sealing the specimens in evacuated or inert-gas filled Vycor glass or quartz tubing. In most cases the investigators imply that the samples are placed in direct contact with the walls of the capsule , ^ 9 »2 5 ,2 6 ,2 7 ) in others, the samples have been wrapped in coluffibium^^*^^ in molybdenum,^ 9 »3 0 ) in titanium^l) before sealing. . 2 4

A few trials were made during this investigation to evalu­

ate the possibility of heat treating without sealing the specimens in

glass. It was soon learned, however, that heating directly in the

furnace tube was feasible only for very short periods (5 - 60 minutes)

and, then, only when hon-porous furnace tubes were available and were

arranged to provide a completely gas-tight system. The use of a

titanium enclosure for the specimens was also tried by forming a

"can* from l/l6 -inch sheet. After the sides and bottom of the can

had been formed and joined the samples were placed inside and the

top was welded in place. A small plug had previously been welded to

the top and a l/8 -inch diameter hole had been drilled through the plug and top. The closed can was then placed in the arc melting

furnace. The furnace was evacuated and flushed with helium several

times. I'inally the system was filled with argon whose pressure was

adjusted to that required to produce one atmosphere at the heat treat­

ing temperature. The arc was then struck and the hole in the plug

closed by welding* The can and samples were heated for 48 hours at

1 0 3 0 -C. and water quenched. However, the heat treat conditions were

too severe from the standpoint of oxidation of the l/l6 -inch sheet.

Since no other materials were available this method was abandoned.

When the first two methods failed to provide satisfactory protection, provisions were made to seal the samples in Vycor. The necessary apparatus consisted of a three-stage oil diffusion pump backed by a mechanical pump. The diffusion pump was connected to a length of Pyrex tubing which served as a manifold. At one end of the 25 manifold was a stopcock.to allow cutting the pumps off from the rest

of the system and at the other was a graded seal to which the cap­

sules were attached. Entrances were made at -various places along

the manifold for a mercury manometer, a gas inlet, an air inlet and

aii ionization gage. The arrangement of this apparatus is shown

schematically in Figure 4.

Specimens to "be heat treated were carefully cleaned and

dried in acetone. They were then placed in a titanium "boat hent

from l/32—inch commercial sheet. Boat and specimens were placed in

a length of cleaned Vycor sealed at one end. The Vycor was mounted

in a glass blower*s lathe and "necked—down” at a suitable position

to form the capsule. Usually several capsules were prepared at one

time in which case a second set of specimens and boat were inserted

in the same length of tubing, the tubing necked-down, a third set in­

serted and so forth. The Vycor was then attached to the pumps at the graded seal and the pumps started. After the pumps had operated for about an hour the capsules were thoroughly flamed, taking care to avoid oxidizing the specimens. Flaming was continued until it produced no appreciable increase in the reading of the ionization gage. The pumps were then cut off from the system and argon (9 9 . without further purification was admitted. (The first capsules were filled with helium but collapsed after a short time at high temperature. It was reasoned that helium was probably diffusing through the walls of the tube so the gas was changed to argon. This experience has also been shared by other investigators according to a recent report.(32) 2.6 pressure of the argon was adjusted, to 1 7 to 2 6 centimeters of mercury- depending on size of the capsule and heat treat temperature. The final operation was, of course, the actual sealing and removing of the capsule. Three sizes of tubing were used for the capsules: 9 mm.,

19 mm., and 25 mm. outside diameter. In capsules of the 9 mm. tubing the specimens were not shielded "by a titanium "boat since they were used only for melting temperature determinations or low—temperature equilibrations.

Furnaces

For heat treatment In the temperature range 850°C. to 1025°C. two Globar horizontal tube furnaces were used. These furnaces were equipped with indicating controllers and tapped transformers for vary­ ing the input voltage. Temperature indication was provided by noble metal thermocouples placed in the hot zones of the McDanel refractory furnace tubes. However, checks on the furnace temperatures made by placing on the "floor" of the furnace tube a platinum—platinum 13$ rhodium thermocouple attached to a Leeds and Horthrup portable potenti­ ometer showed the indicated temperature to be low by amounts up to approximately 100CC. Also, the temperature fluctuated +2 0 °G. around the control point during on-off cycling of the controller. The error in the indicated temperature was avoided by using the "check thermo­ couple to establish each heat treat temperature. The amount of fluc­ tuation around the control point was reduced by adding "thermal inert la'1 or "ballast" to the hot zone of the furnace. This "ballast" was in the form of two—inch diameter steel bars suitably arranged to accomodate 2 7

. the capsules. The Junctions of the controller thermocouples were

inserted in small holes near the periphery of the ballast bars while

the check thermocouple was pierced at the centers of the bars. B y

this means the fluctuation was reduced to a maximum of + 1 0 °C.

Refractory plugs were shaped for each end of the furnace

tubes so that an argon atmosphere could be maintained around the

capsules during heat treatment.

Equilibration at temperatures from 650°C. to 800°G. was

performed in four small tube furnaces. These furnaces were connected

to the 115—volt line through autotransformers. No instruments of any

type were available for automatically controlling the temperatures

of these furna,ces. Chromel-alumel thermocouples were placed at the

center of the hot zone in each furnace and connected to a switching

device. A Leeds and Northrup portable potentiometer was attached to

the switch for determining furnace temperatures. The maximum devia­

tions from the desired temperatures were of the order of + 1 0 °G. as a result of changes in line voltage.

Por melting temperature determinations a high—temperature resistance furnace was used which was similar to that described by

McRitehie and Ault^-^ and by Pew and Manning.(3**) This furnace con­

sisted essentially of a cylinder six—inches inside diameter by twelve

inches long closed at the top and bottom by flat plates. Molybdenum foil 0 . 0 0 3 and 0 .0 0 5 -inch thick rolled to a cylinder one-inch in diameter by 1 1 inches long formed the heating element. Suitable connections for gas and vacuum lines were provided. All internal 2 8

surfaces of the furnace were silver plated and additional radiation

shields were provided by four concentric cylinders of molybdenum

sheet five inches long placed at the midpoint of the tube. All

joints were sealed by O—ring gaskets. Capsules were supported on a

ceramic cylinder in a vertical position at the middle of the element.

The capsules could be observed through a glass window in the wall of

the furnace by sighting through l/8 -inch diameter holes in the radia­

tion shields and through a l/l6 -inch vertical opening in the furnace element. Water cooling coils were soldered to all exterior surfaces of the furnace.

Power was supplied to the furnace through an auto transformer and a 10:1 SEVA transformer. Temperature was regulated by manual oper­ ation of the auto transformer. Power requirements for l450°C. in vacuo were of the order of 450 amperes at 5 volts. Meters were connected to the various components to indicate the amperage and voltage at which they were operating. Details of the apparatus may be seen in Pigure 5*

It was first believed that it might be possible to make accurate determinations of the solid-liquid reaction temperatures of the alloys by direct observation of the melting of suitably shaped specimens through an optical pyrometer. A few trials proved this method to be impractical because the rate of evaporation of the alloys above 900°C. was high enough to deposit a layer of metal on the walls of the capsules which obscured the specimen prior to the start of melting. Consequently all melting determinations were made by visual or metallographic examination of specimens upon their removal from . . ‘ ' . ■ 29

the capsules after heat treatment at various temperatures. These

temperatures were determined by means of a previously calibrated platinum-platinum 10$ rhodium thermocouple whose hot Junction was

situated Just above the capsule inside the furnace element. The thermocouple was attached to a Leeds and Korthrup portable potentiom­ eter by compensating lead wire. Entrance to the furnace was provided by a Stupakof seal.

To determine how closely the thermocouple readings repre­ sented the specimen temperatures several checks were made against the melting point of gold. Small wedge-shaped pieces, of pure gold foil were placed in the furnace in the location and manner of the alloy test specimens. The temperature of the furnace was slowly raised while observing the gold through an optical pyrometer and taking millivolt reading on the thermocouple potentiometer. The observed gold points were sharp and reproducible. The results of these checks indicated that, when the furnace was in a condition of thermal equi­ librium, the thermocouple indicated specimen temperature to within

± 5°F.

Heat Treat Schedules and Quenching

All alloys were first heat treated to homogenize the cast structures. Suitable specimens ifere then cut from the homogenized buttons and equilibrated at various temperatures and times following the procedures heretofore described. The objective in the selection of the various time—temperature relationships was, of course, to promote as complete homogenization or equilibrium as possible but to 3 0 do so at times and temperatures which would minimize chances for contamination. Final choice of the combinations used was guided by experience of other investigators in somewhat similar systems

(Ti—Hi, Ti—Fsj Ti-Cu, etc.) ^2,26,30,35) experience in this system as data were accumulated. In general the schedule shown below was followed although complete details for the treatment of each alloy are given in tabular form in the Appendix.

temperature Time (Degrees Centigrade) (Hours)

1 0 2 5 (homogenization) 7 2 1 0 2 5 (equilibration) 8 975 8 9 3 0 (homogenization) 7 2 9 3 0 (equilibration) 1 2 900 24 850 72 800 1 6 8 750 267 7 0 0 3 6 0 6 5 0 5 1 0

To promote homogenization and equilibration, certain of the low—cobalt alloys were cold worked prior to heat treatment. The

■working was accomplished by compressing the buttons or sections cut therefrom on a Tinius Olsen Tensile Testing Machine up to the capacity of the equipment or until the onset of severe cracking. Details as to the amount of working and the behavior of the alloys are given in the Appendix.

Following heat treatment the alloys were quenched, usually by submerging the capsule in water and crushing it with a pair of tongs. In a few instances it was wished to check the soundness of the capsule after heat treatment or to avoid oxidizing the surfaces of the specimens "by reaction with the quench water in which cases the capsules were air quenched or water quenched without crushing. EXAMI EAT I OE AHD ANALYSIS Off ALLOYS

Me tall ographic Technique

Sor metallographic examination, all specimens; were first mounted, in a Bushier thermo—setting plastic. Bough grinding was performed on a 1 2 0 —grit halt followed by hand grinding on 2*K), *K)0 and 5 0 0 -grit silicon carbide papers used wet. Initial polishing was accomplished with 6 0 0 -grit silicon carbide in a soap and water suspension on a wax lap. Pinal polishing was done with ,1ShamvaM

(an extremely fine magnesium oxide) on nGramal" cloth on a low-speed wheel. Most of the harder alloys (above 20$ cobalt) polished readily with the above technique and some of the hardest alloys

(38 ~ 5 0 $ cobalt and 60 — 6 8 $ cobalt) polished rapidly with rouge and Buehler*s "Miracloth” on a very high speed wheel. However, considerable difficulty was experienced with the softer alloys

(o - 10$ cobalt). A number of different cloths, laps and compounds were tried before the right technique with the above procedure was perfected to the point of yielding surfaces even moderately scratch free .

A number of investigators have reported excellent results from electropolishing titanium alloys.^37,38*39,^1) All but one of these involve use of perchloric acid which can be hazardous.

Accordingly, only Findlay1 s solution (anhydrous zinc and aluminum chlorides in n—butyl and ethyl alcohols) was investigated. When the procedure worked, an excellent, scratch-free, slightly-etched surface was obtained. More often it did not work and a scratched and severely pitted surface was the result. Part of the difficulty seemed to he inherent in the very small size and irregular shape of most of the specimens which made it hard to control current density on the Buehler Electropolisher. Also, the use of low-melting alloy in place of screws and other devices (a substitution which seemed to be dictated by the nature of the specimens and mounts) to form electrical contact between the electrode and the specimen caused excessively high cell voltages at the required current densities.

Pinally, the electrolyte was stable for only a week. Although the production of surfaces free of scratches and distorted metal was claimed for the electropolishing method, it was not used for this investigation because of the difficulties described.

The polished specimens were etched for microscopic examination with one of the following etchants:

a. aqueous solution of 1 — 2 ^ HE acid

b. aqueous solution of 2 % HP acid, 2$> HHQ^ acid

c. aqueous solution of 2^ HP acid, 2% H 2 O 2

The specimens were examined microscopically at various magnifications in the etched and unetched conditions by direct illumination on standard metallurgical microscopes and on a Reichart metallograph.

Limited use of polarized light was also made in the examination of certain alloys to distinguish the beta phase• (37*^2) Conventional techniques were employed for photomicrography. 34-

X-Ray Diffraction

Samples for x-ray diffraction analysis were prepared

from various alloys either "by filing a carefully cleaned specimen

or crushing in a mortar. The filings or powders were screened on

a 325—mesh seive. Prom the minus 325-mesh portion of the screenings

a filament was prepared by mixing it with a hinder (Duco cement) and

forcing the mixture through, an extrusion die. The filaments were

about 0 .0 1 0 -inch in diameter.

Diffraction patterns were obtained from the powder

samples using either a North American Phillips or von der Heyde

camera of the Debye—Scherrer type. Diameter of the cameras was

approximately 114 millimeters® The Straumannis asymmetrical film mounting was used. Cobalt characteristic radiation filtered with

iron or molybdenum radiation unfiltered and filtered with zirconium were used. The films were measured on a Jarrell-Ash film scale to

the nearest 0 . 0 5 millimeter.

The Bragg angles were calculated from the film measure­ ments in a conventional manner. A correction factor for film shrink­ age was determined either from the distance corresponding to O^qq ~ °o

or from fiduciary marks made by overlapping the ends of the film in

the camera. Corrected Bragg angles were converted to interplanar

spacings by means of Bureau of Standards Tables^ 6 ) which are based

on new characteristic radiation wavelengths adopted at the 1946

Internetional Conference. Since the spacings in these tables are based on K-alpha-one radiation only, certain calculated nd M values 3 5 were converted to K-alpha, K-alpha-two or K-beta by applying an

appropriate correction factor. Inasmuch as the diffraction re­

sults were to he used primarily for phase identification rather

than accurate determination of lattice parameters, only one meas­

urement was taken of each line position and corrections for absorp­

tion, eccentricity, etc. were omitted.

Chemical Analysis

The raw materials used for melting stock were analyzed

spectograpkically for metallic impurities by an independent labor­

atory. They were analyzed for gaseous impurities by the vacuum

fusion method in a manner similar to that described in the liter- ( /di) ature in the laboratories of the Titanium Alloy Manufactur­

ing Division of The National Lead Company.

All alloys from 1 — 18$ cobalt and some alloys above 18$

cobalt were analyzed for titanium content in the Analytical Division

of the Engineering Experiment Station, Ohio State University. A few alloys selected at random were also analyzed semi-quantitatively

for copper and tungsten. The analytical procedure consisted essent­

ially of

a. dissolving a 0 . 2 to 0 .3 —gram sample in sulphuric ac i d ;

b. eliminating the cobalt by electrolytic deposition

in a mercury cathode cell;

c. precipitating the titanium with hydroxide; . 3 6

d. igniting the filtered titanium hydroxide to titanium

dioxide and weighing.

The percentage titanium content was calculated from the weight of

titanium dioxide and the original sample weight. The cobalt content

was taken by difference.

Hardness Determinations

The hardness of the various alloys and test buttons was

determined on a Vickers Hardness Testing Machine using a 1 0 -kilogram

load. The diagonals of the indentor impressions were measured with

the machine microscope using a micrometer eyepiece and a 2 /3 -inch

focal length objective. Most of the alloy specimens had been mounted

and polished for microscopic examination and were still in their

metallographic mounts when the hardness measurements were made. Un­

mounted specimens were ground on a 1 2 0 -grit belt to provide reasonably

smooth and parallel flats for the hardness tests.

Sesistivity Measurements

It has long been recognized that the specific electrical

conductances of alloys in a binary system depend upon the composition

of the alloy and the temperature of measurement. It has also been

recognized that the conductance (or resistivity) varies in a charac­

teristic manner with composition or temperature depending on the number

and types of phases present under equilibrium conditions. Although

this phenomenon has seen relatively little application during the 3 7 past few decades in the vast amount of work: performed on alloy

systems, two recent authors have hailed it as a very useful anal­

ytical technique, claiming for it a high degree of sensitivity in

the detection of phase changes.^^'^^ This sensitivity is said

to he inherent in the abrupt change of slope and, frequently, the

abrupt change in curvature occurring in the resistivity isotherms

or temperature-resistivity curves at phase boundaries.

In an attempt to apply the resistivity technique in this

investigation the necessary instruments were collected and installed

as shown in Figures 7 and 8 . Specimens were approximately 2 x 2 x 15

millimeters in size and were polished to as nearly uniform cross-

section as possible. The specimens were mounted for room—temperature

measurements in a fixture containing insulated, current contacts and

two probes mounted at a fixed distance of 1 3 »5 ± 0 . 1 millimeters.

The probes were connected electrically through suitable switches to

a Type 7552 Leeds and Uorthrup Potentiometer with an external gal­ vanometer. In series with the test specimen was a standard resist­

ance so arranged in the circuit that the voltage drop across it

could also be measured with the potentiometer.

The steps in the operation of the equipment for a

resistivity measurement were as follows:

a. adjust current in circuit to approximately one ampere by means of paralleled variable resistors;

b» measure voltage across standard resistance (Es^);

c. measure voltage across test specimen (E_ ); X 1 3 8 d. reverse position of "ganged” switches, thereby reversing direction of current flow while maintaining correct polarity at the instruments, and measure voltage across standard resistance (SS2) and across test specimen (E-^g).

From the ratio ^ * Rxl and were computed. The 21 21 average of and was taken as the resistance of the test specimen. The resistivity was then calculated from the relation rho (microhm-centimeters) = where R = resistance in microhms; Xr A = cross-sectional area in

square centimeters;

Ii = length in centimeters. 3 9 RESULTS ASH) DISCUSSION

PreT>arat±oa of Alloys

In general, the final arc—melting arrangement performed

satisfactorily. The chief objections were concerned mainly with, the fact that the electrode position could not always he observed during melting (or while striking the arc) which frequently led to the ingot1 s becoming attached to the electrode tip. Such ingots were, of course, discarded because of the probability of having added considerable tungsten to the alloy.

As shown by the chemical analysis (Table II in the Appendix) the composition of the cast alloy was in nearly all cases reasonably close to the intended composition. Such variations as did occur were caused by one or more of the following factors:

a* Evaporation of the molten metal under the arc and physical expulsion by the arc of small pieces of the charge and of the molten alloy from the melting area. The total loss from these effects was estimated to be approximately lj£ of the weight of charged metal •

b. Loss of small pieces of metal while transferring the charge to the furnace.

c. Loss of metal in the saw kerf when cutting the 10—gram buttons for uniform melting.

As will be seen by examining the representative photo­ micrographs of the as-cast structures contained in the Appendix, sufficient heat was available in the arc and the melting procedure was adequate to produce thoroughly-melted alloys in nearly all cases.

Possible exceptions to this statement may be the alloys containing more than 5 7 % cobalt. A description of the phases present in each as—cast alloy is given in Table III in the Appendix.

While the subject of gaseous contamination of the melts will be covered at some length in subsequent discussion of particular alloys, it is in order to mention here that the operation of the fur­ nace in this respect appeared satisfactory as Judged by simple methods of evaluation. Repeatedly in the course of preparing the alloys,

test buttons of unalloyed titanium were melted under standard conditions •

The hardness of these test buttons was usually higher by 5 to ? Vickers

Uumbers per melting than that of the melting stock. (A hardness in­ crease of 10 Vickers numbers per melting is usually considered indica­ tive of satisfactory melting practice by persons more experienced in titanium technology). It must be pointed out, however, that it is difficult to obtain for reference purposes a representative hardness of the titanium melting stock because of the intergranular and grain boundary voids inherent in the as—deposited crystal bar. Also, in one or two cases where the test button was remelted, the hardness after the second melting was 1 to 2 Vickers Numbers lower than after the first. The hardness increase accompanying the first melting had been of the order of 15 Vickers numbers. Whether such results should be attributed to the difference in surface area between the crystal bar and the melted button (with attendant differences in volume of i n adsorbed gases) or to inconsistencies in the operation of the furnace is not definitely known.

Homogenization and Equilibration

The various procedures employed in the heat treatment of the alloys were generally satisfactory* The micros true tures of the homogenized alloys, typical examples of which are shown in the

Appendix, indicated that, when the alloying practice produced thorough­ ly melted ingots, the tirae-temperature schedule for homogenization was adequate. Such conditions as dendritic coring and presence of non- equilibrium eutectic mixtures and incomplete peritectic reactions appeared to be completely eliminated. The heat treat schedule for homogenization and the phases in the resulting micro structures of each alloy studied are listed in Table IV in the Appendix.

Since the investigation of the kinetics of the various phase reactions did not fall within the scope of this program, no attempt was made to evaluate quantitatively the effectiveness of cold working the alloys prior to heat treatment. However, the qualitative consider­ ations regarding the benefits of cold work in promoting phase changes are none-the-less valid. Results of this investigation indicate that, because of the omnipresent menace of contamination, the lowest possible heating temperature and the shortest possible time should be employed - even to the point of falling short In some instances of obtaining ideally perfect equilibrium. In future work it would be recommended that low alloy samples be cold worked as severely as possible (rolling 4 2

the compressed ingots into thin sheets would, be ideal) to meet the above objectives.

While no systematic study was made of the response of

titanium-cobalt alloys to cold working, the work did indicate that homogeneous alloys of 1 to 8 ^ cobalt would withstand at least 755^ compression. Alloys of 1 to 4^ cobalt undoubtedly could be rolled readily. These results constitute a semi—quantitative extension of the data of Craighead, Simmons and Eastwood^0^ who reported that alloys if 3 ^ cobalt were readily hot—forged and hot—rolled and the report of Kroll^*5"8) that alloys of 9 $ cobalt could be hot—rolled.

Before leaving the subject of cold working it should be noted that its use on samples which are to be equilibrated is not always entirely beneficial. In certain cases, as in determining the beta/(alpha 4* beta) solvus, distinguishing between grains recrystal— lized at the equilibration temperature and one of the phases in the equilibrated structure can be confusing. Another example of a pro­ cedure producing microstructures difficult to Interpret might be found in the case of a cold-worked sample heated just below a eutectoid de­ composition and just above the recrystallization temperature.

Sealing the specimens in Yycor capsules is undoubtedly the most practical method of protecting the samples during heat treatments at temperatures up to 1 1 0 0 °C. Several precautions should be observed, however. Since the glass seals on the ends of the capsule are not always perfect and. since they are easily broken or cracked, several duplicate samples, each sealed in a separate capsule, should be run 4*3 whenever possible* Although the practice was employed in this study

because of the limited furnace capacity available (necessitating use

of very small diameter capsules) » samples should not be placed in

direct contact with the capsule walls. There was evidence that even

at temperatures as low as 7 0 0 °C. there was some reaction between the

titanium and the glass.

The use of titanium sheet to separate the specimen from

the glass appears to have been moderately successful. In a few in­

stances considerable reaction between the titanium separator and the glass was observed. Early in the program a few tests were made to

evaluate the effectiveness of molybdenum sheet as.a protective cover­

ing for the samples. The results obtained from the small amount of

sheet available showed the molybdenum to be effective although some

indications of alloying between specimen and sheet were observed. It

is now believed that samples: could be safely wrapped directly in moly­ bdenum for relatively low temperature work and that a titanium spacer could be placed between the sample and the sheet to provide optimum protection for heating at higher temperatures.

Determination of Beta/(Alnha Beta) Solvus

The procedure consisted simply of heating alloys of different

cobalt contents at various fixed temperatures below the allotrotropic

transformation for pure titanium until phase equilibrium was attained.

The specimens were then quenched and examined metallographically. The details of the thermal treatments and of the resulting microstructures are given in Table V. Typical micro structures are shown in Figures

3 6 and 3 7 . The me tallographic phases which are involved in this determination are "alpha" or "equilibrium alpha", "transformed alpha"

and "retained beta". By "alpha" or "equilibrium alpha" is meant the

low-temperature or hexagonal close-packed modification of titanium

(or titanium solid solution) which can exist or has existed as an

equilibrium phase under suitable conditions of temperature and alloy

composition.

Throughout this thesis the term "transformed alpha" will be applied to a widmanstatten microstructure formed by transformation

of the beta phase during cooling. No attempt will be made to categor­

ise the transformation-produce, "transformed alpha", as "stable alpha"

or "metastabile supersaturated alpha". The significance of the struc­

ture for the purposes of this investigation is that it indicates that all or some portion of the alloy in question existed as the equilibrium beta phase during the prior thermal treatment.

The term "retained beta" refers to the higher—temperature, body-centered cubic modification of titanium or titanium solid solu­ tion. It indicates that the alloy content was above the "critical alloy content" required to suppress the beta transformation or decompo­ sition during cooling. It will be noted from the data in Table V that the "critical content" for titanium-cobalt alloys lies between six and seven percent cobalt. This is in agreement with the findings of (cc) McQuillan who predicted that the beta transformation would not be suppressed in alloys of less than about 6% (5 atomic—percent) cobalt. 4-5

The manner in which the above-described data serves is readily recognized by considering the data in Table V for some iso­ therm such as 750°C. It is seen that as the alloy content of the specimens increases from h to 6$ cobalt the phases coexisting at temperature (alpha and beta) do not change but the relative amount of alpha steadily decreases. Beyond a composition lying between 6 and

7$ cobalt the thermodynamic equilibrium requirements change and the two phases can no longer coexist. Accordingly, the 7$ cobalt alloy shows a microstructure of 100$ beta phase.

Determination of Beta/(Beta + TjgCo) Solvus

The details of the procedure for this determination are as described in the preceeding section. Pertinent data on thermal treat­ ment and microstructures are given in Table VI. A representative micro structure is shown in Figure 38. The characteristics of the Beta phase have already been described, discussion of the structure of the compound TigCo, and of the 11 three phase'1 alloys will be presented later.

Determination of Beta-TigCo Butectic Temperature

The equipment and procedures for making these determinations have been previously described in the section on "Furnaces". For most of the alloys tested, the amount of liquid formed at temperature was sufficient to cause the liquid to run down into the bottom of the cap­ sule. Under these conditions evidence of having exceeded the eutectic temperature was unmistakable and a reasonable approximation of the amounts of the two phases could be made by visual examination of the

quenched specimen. 4 6

Where the degree of melting was very small or Hincipient”, the specimens were examined metallographically. These results were doubly rewarding for they made it possible to locate the eutectic re­ action within a narrow temperature range and they served as a check: on the previous interpretations of the corresponding as-cast struc­ tures.

Pertinent data are listed in Table VII and a typical micro­ structure is shown in Figure U-Z.

Determination of TjgCo - TjCo Peritectic Temperature

The comments in the proceeding section apply to this deter­ mination as well for the procedure and objectives were the same. Data are given in Table VIII and a representative microstructure is shown in Figure h3*

Verification of Sutectoid Decomposition

Included among the samples studied to determine the two

Solvus Dines are a number which were expected to bracket the eutectoid reaction isotherm (those treated at 7 0 0 °G. and lower)• (The details of the treatments are given in Tables V and VI), It was also expected that the microstructures of the decomposition products would display a marked similarity to those in other systems such as the Ti-Fe. This decomposition product usually occurs at the grain boundaries and has an appearance similar to nodular pearlite.

The most promising micro structure obtained were those shown in Figures 39* ho and. hi which bear little resemblance to the expected structure but which could represent an agglomeration of what was originally a fine eutectoid Ti2 Co.

In an endeavor to identify the phases present an x-ray diffraction pattern was obtained from a specimen taken from Alloy

I9C163D* The interplanar spacings for this pattern are given in

Table X. To establish the phase Identities, these spacings were com­ pared with all available data fro all phases in the Ti-Co and TiO systems. The best match, and, that, none—too-certain, was obtained with ASTM data for alpha-titanium.

Conflicting evidence was introduced by the micro structures for the remaining samples in this group of which Figures h 5 and

*4-6 are typical. It appears likely that the matrix in each case con­ tains two different phases. This is particularly plain in Figure ^-5*

In as much as the matrix turns dark with the peroxide etch and light with the nitric acid etch it is presumed to be beta phase.

X-kay diffraction data for Specimen I8 C1 6 3 E (Figure 4-5) are presented in Table IX. Here again the results are inconclusive, the best agreement being with alpha and beta, titanium with two lines unassigned.

It appears, unfortunately, that the results obtained do not furnish incontrovertible evidence for the eutectoid decomposition and the temperature therefor. However, it is proposed that the data do furnish opportunity for deducing in the following certain information of value.

a. It is known that all specimens in the group had a 1 0 0 $ beta microstrueture prior to equilibration* 4 8 ‘

b. The etching characteristics of the etchants used suggest that the alloy matrix in Figures 39, 40 and 41 are not beta and that beta is present in alloys shown in Figures 44, 45 and 46.

c. X —ray diffraction data, while inconclusive, indicates the presence of alpha and beta phases in specimen I8 C163B — which con­ dition would apply equally well for 190170® and H 0 C1 6 8 H (Figures 45 and 46). They also indicate the presence of the alpha phase in specimen I9C170D.

d. The microstructure of the 9$ alloy heated at 675°C. may represent a mixture of alpha plus beta or of alpha plus TI2C 0 .

Consider the results of Long, and other s^^, from their study of oxygen—contaminated titanium-nickel alloys. They have shown that the effect of oxygen was to raise the beta to alpha plus beta and the beta to beta plus gamma transformation temperatures. Below the regions of alpha plus beta and beta plus gamma equilibrium lies an extended ternary region of alpha plus beta plus gamma stability.

The temperature of the binary eutectoid isotherm (alpha + beta + gamma to alpha + gamma in the quasi-binary system) does not appear to have been appreciably affected by the introduction of oxygen.

It appears reasonable to assume, then, that the phases in

Figures 39» 40 and 4l are alpha plus Ti2Go.

e. It is further suggested in view of the work of Long cited above that the structures in Figures 44, 45 and 46 are the possible result of oxygen diffusion along the grain boundaries of structures which were essentially 1 0 0 $ beta throughout most of the equilibration. Zj-9

The oxygen diffusion gradually produced a ternary equilibrium of alpha 4- beta + Ti2 Co.

If the foregoing be reasonable one may conclude that the

I9 C1 7 0 B and I9 C1 7 C® specimens represent material which, when free of contamination, would have had a 100 $ beta structure and an alpha + gamma structure, respectively, thereby placing the eutectoid temper­ ature between ?00 and 6 7 5 °C.

Determination of the Crystal Structures of the Various Phases

Confirmation of the crystal structures previously reported for alpha titanium, beta phase and TiCo were readily obtained.. Ho attempt was made to determine lattice constants from the alpha titanium patterns since phase identification only was of interest. o A parameter of 3-21 A was consistently obtained for the cell size of the beta phase. Since this value was obtained for specimens lying in the beta + Ti2 Co region of the diagram it represents the con­ dition of maximum solubility at 930°0. (13$ cobalt). This compares to C 7^ ) a value of 3 * 3 0 6 reported for pure titanium at 9 0 0 °C. o Values of 2.98 to 3»00 were obtained for the cell size of

TiCo from several specimens. All lines were readily indexed on the basis of a body—centered cubic structure. Lattice parameters corres­ ponding to interplanar spacings obtained from a 5 2 $ cobalt alloy are shown in Table XII. These results are in agreement with those reported by Duwez and Taylor^ .

Being aware of the conflicting data and opinions recorded in the literature for the correct structure of the compound TigCo, 5 0

(see Literature Survey), every conceivable extra precaution was exer­

cised in the Preparation of alloy I38C154A. The melting furnace and

the charge were cleaned with extra care and the furnace flushed repeat­ edly. A titanium getter-button was held molten for 15-30 seconds before each melting of the alloy. An average hardness increase of 11

Yickers Numbers per melting occurred in the getter button so it is reasonable to accept this as an indication of the maximum gaseous con­

tamination of the alloy.

Por homogenization pieces of the cast button were inserted in small holes in titanium plugs made from 5/8" diameter rod. The plugs were sealed in the glass capsule in the usual manner. The as- cast micro structure for this alloy can be seen in Pigures 1? and 18 and

the homogenized structure in Pigure 32. While the chemical analysis of

this alloy (Table II) shows it to be considerably below the composition for 100$ TigCo (3 6 .3 2 $ vs. 38.15 required) ~ which results are sub­

stantiated by the structure in Pigure 32, that fact would not lessen its usefulness for x—ray study provided the alloy were homogeneous.

X-ray diffraction patterns were prepared from the 38$ alloy as-cast, homogenized at 9 3 0 ®C« for 48 hours and for 96 hours. Powder patterns were also obtained from a number of other alloys known to contain TigCo (see Table XII, for example). In all cases the patterns showed the same structure. The pattern obtained from the as-cast 38$ alloy contained fewer and more diffuse lines. The 96 hour heat treat­ ment produced only a slightly better resolution in the back reflection region as compared to the 48 hour treatment. 5 1

The diffraction data for specimen I38C15^A are presented

in Table XI where they are compared to similar data for TigNI pub­

lished by D w e z and Taylor^-*) , It will be noted therein that the

agreement between the W o sets of data is very close, particularly

with respect to “missing" or "extra" reflections. The cell size cor­

responding to this data for the 3 8 $ cobalt alloy is a 0 = 1 1 . 3 0

If the conclusions of Earlsson^^*^^ and, In particular,

Eostokervoo/ are correct, the structures determined in this investi­

gation correspond to Ti^Cog0 and not TigCo. The implications In the

reports of those investigators are that the oxygenated compound can

exist with a deficiency of titanium (Ti^Co^O) but not with a deficiency

of oxygen. That being the case, the generalization would follow that

all or nearly all of the alloys studied in this investigation con­

tained at least l^f- atomic percent oxygen. While isolated instances of

contamination have been observed the data obtained from the balance of

the alloys completely invalidate this hypothesis.

Further, the two proponents of the I’e^W^G structure are not

in agreement. Eostoker reports the same structure for Ti 2 Cu and Ti^CugO while Karlsson records different structures. Karlason states that a

structure corresponding to Ti^CrgO does not exist, whereas Wang,

et a l ^ ^ have reported it (or Ti-^Cr-jjO which is isomorphous). Eostoker

compares indexed "d" spacings for a Ti^I’e20 with Taylor1 s^ ^ values

for a Ti ^ e to show the equivalence of the two structures and includes

diffraction lines, which Taylor does not report, indexed for reflections

which are usually understood to be extinctions for a face-centered cubic 5 2

structure (332 , 5 0 0 , 430, 431, 821). Neither does Rostoker give any details of his melting and heat treating technique nor chemical anal­ ysis results for the alloys studied*

In. short, there is no satisfactory explanation of the results of this investigation with respect to other results obtained for the structure of Ti2 Co. No pattern for the Ti2 Co phase corresponding to the MgCug structure was found so, since no vacuum fusion analyses for oxygen were performed on any of the alloys it can only he inferred that the Fe^jW^C structure for Tij^CogO can exist without oxygen or with a deficiency of oxygen.

X—ray diffraction data for specimen I6 8 GI77A are given in fable Xiii and corresponding data from the literature are given in

Table XIV, Chemical analysis of this alloy (Table II) showed it to be

3 *3 $ below the 7 1 .1 ^ cobalt calculated to provide a structure of 1 0 0 ^

TiCo2 * The microstructure of the as-cast alloy is shown in Figure 2 2 .

The microstructure of the homogenized alloy is shown in Figure 35*

The x-ray results agree with the metall©graphic results in that both show nearly equal amounts of two phases. The x—ray pattern was readily interpreted by eliminating the TiCo lines and indexing the remaining lines on the basis of an MgCu^ structure (face-centered cubic).

This structure, then, agrees with that reported by Wallbaum^1^ as a cobalt—poor phase whereas Duwez and Taylor^^3) found the same structure

(hexagonal) to exist at compositions on both sides of TiCo2 »

A possible explanation for this disagreement may be found in the photographs. Figure 22 shows a few small dendrites of a high 5 3 melting third, phase. This phase is not seen in the microstructure of the homogenized a l l o y (Pigure 35) it might he that solution of this impurity altered the structure of the TiCo2 phase.

The Phase Diagram

The phase diagram, for a portion of the Titanium-Cobalt

System is presented in Pigure *!•?. The diagram was constructed on the basis of data obtained during the course of this investigation. Al­ though the important aspects of these data have been discussed earlier in this report, a few points concerning their graphical representation may be required. M c Q u i l l a n * 77) value of 882+ 1 °C. for the allotropic transformation temperature of titanium was used. The intersection of the best possible curves through the data for beta/(alpha + beta) and beta/(beta plus gamma) solubilities indicated a eutectoid decomposition was not obtained, it was believed that the indirect evidence was suf­ ficiently strong to Justify drawing the eutectoid reaction isotherm at 685+ 10°C.

Both the peritectic reaction isotherm at 1055± 5°C. and the eutectic isotherm at 1 0 2 0 + 5 °C. were sharply defined by the data from the melting point determinations.

The selection of 27$ cobalt as the eutectic composition was an approximation based on as-cast microstructures and melting data for alloys in the 2*1— 3 2 $ cobalt range.

The maximum beta solubility was estimated to lie between

1 6 $ and 18$ cobalt on the basis of the as-cast microstructures for these alloys and on the basis of the results from heating these 5 4 alloys to 1025°C. The final ■value of 17$ cobalt was determined by

the shape of the beta/(beta + TigCo) aolvus.

Although no data on. the alpha titanium solubility limit were obtained during this investigation (McQuillan estimates it to be less than 0 .6$ ) ^ ^ , an area was indicated by dotted lines for

compliance with the phase-rules.

Ho attempt was made to indicate the character of the diagram beyond 55$ cobalt because it was felt that the evidence was inconclusive.

In Figure 48 is shown a comparison of the effectiveness of various solute elements on the lowering of the beta—to-alpha transfor­ mation temperature of titanium. The data were obtained from the- dia­ grams published in the indicated references. McQuillan has stated

that if the transformation temperature for binary alloys of 1 - 5 atomic percent Co, Cr, Mn and Hi (as determined by his experiments) were plotted versus atomic percent solute all the data would fall on a single straight line. Figure 4-8, then, serves to illustrate the relative effectiveness of several elements, to compare the lowering effect as determined by investigators with that reported by McQuillan, and to indicate the degree of agreement among the different investi­ gators.

It is interesting to note that the effect of cobalt as determined in this investigation is almost linear and that its effectiveness is close to that predicted by McQuillan.

Hardness Peterminations

In Figure 4-9 are presented graphically the data for hard­ ness of the homogenized alloys listed in Table III. This curve shows 55 many interesting features the most significant "being the hardness peaks at 38$ and 68$ cobalt in contract to the minimum at 55% cobalt.

The maximum and minimum occurring between 10% and lM% cobalt also is reported for similarly treated titanium-iron alloys and titanium— chromium systems^0) . In these systems the maximum occurs at a composition well below the eutectoid.

Resistivity Measurements

During the early stages of the program a considerable amount of experimentation was performed on techniques for resistivity measure­ ments*

In the course of these experiments several determinations wers made of the volume resistivity of the iodide titanium melting stock* An average value of b-5.8 microhm-centimeters was obtained which compares favorably with the value of 55 reported by Greiner and Ellis^78)# and the value of h2.1 reported by McQuillan^ 77) # The tech­ nique also proved to be an effective although elaborate method for indicating contamination during melting or heat treating. It was orig­ inally intended to use the technique during the determination of the beta/(beta + TigCo) solvus. However, the specimens for this study were heated to 1025°U* and quenched to aid in accelerating phase transforma­ tion during subsequent equilibration. Unfortunately the quench proved too drastic and the samples cracked too extensively to be usable for resistivity measurements* Before new alloys could be prepared the study was essentially completed by metallographic techniques* 56

^ EE I I 2 Ix TABLE I

Chemical Analysis of Melting Stock (Weight Percent)

Fe Si Hi Mo Cu A1 Mn H 0 N

Iodide Titanium 0.01 0.003 ♦ 0.01 0.02 0.005 0.005 0,007 0.025 0.005

0 005 # 0.005- Cobalt** 0.01- . - 0.05- 0.001- 0.005- 0,1 0.05 0.5 0.05 0.01 0.05 0.0012 0.02? 0.007

* Not Determined

** «fypicalH analysis furnished by manufacturer shows 99.5$ Go; 0.3$ Ni; 0.1$ Fe; balance, trace of Si, Ca, Mh. 58

'TABI/E II

Chemical Analysis of Alloys

Alloy Composition (Weight percent) Designation** fi • Co* Cu ' W

I1 C156 98.91 1.09 none none I2C160 98.03 1.97 —— I3C161 96.66 3.34 —— l4Cl62 95*89 4.11 - - I5C166 95*01 4.99 none none I6 CI67 93*93 6 .0 ? - — 170165 92.99 7.01 -— I8C163 91.96 8 . o4 - - 190170 90.25 9.75 - — I1 0 C168 89*76 10.24 — - I12C151 87.80 12.20 - - Il4Cl42 86.18 13-82 - - I16C149 83.70 16.30 — — I1 8 C152 82.15 17.85 — - 124 CSL27 76.71 23-29 none none I2 8 C138 71.77 28.23 none none 1320131 67.75 32.25 none none I38C154 63.68 36.32 none none 1550171 45.17 54.83 - — 1570174 4-3.51 56.49 — - I68C177 32.19 67.81 none none

* Cobalt Determined by Difference

** The coding in the Alloy Designation indicates the nominal composition. 3Tor example, nl8 Gl6 3 M means that melt number 163 consisted of 8^ hy weight of cobalt; balance, iodide titanium. 59- SABLE III

Miorostructures of As—Cast Alloys

r Alloy Ingot Size Designation (grams) Microstructtire

I1G156 5 Very coarse, aclcular transformed—alpha I2C160 5 Very coarse, acicular transformed—alpha I3C161 5 ' Coarse, acicular transformed—alpha I4C162 5 Acicular transformed—alpha x501 6 6 5 Jive aci cular t ransforraed-alpha I6 CI67 5 Transformed—alpha plus cored, retained "beta 170165 5 Detained heta I8C163 5 Slightly cored retained heta I9C170 10 Cored retained heta I10C168 10 Cored retained heta I1 2 C151 10 Cored retained heta; grain boundary cracks Il4Cl42 10 Cored retained heta 1150149 10 Beta plus heta—TigOo eutectic 1160149 10 Beta plus heta — Ti2 Co eutectic 120 Cl53 10 Beta plus heta — Ti2 0 o eutectic I22C155 10 Beta plus heta — TigGo eutectic 1240127 10 Beta plus heta — Ti2 Co eutectic I26C128 10 Beta plus heta — Ti2 Co eutectic I2 8 C138 10 Dearly 100^ heta — TigCo eutectic I30C130 10 Ti2Co plus heta — Ti2 Co eutectic I32C131 10 Ti2 Co plus heta — T±2 Co eutectic 1340132 10 TiCo *§• peritectic Ti2 Co 4- heta—Ti2 Co eutectic I36C133 10 TiCo 4* peritectic Ti2 0 o 4- heta—Ti2 0 o eutectic 1380154 10 TiCo 4- peritectic Ti2 Co 4- heta— Ti2 Co eutectic 1420157 5 TiCo 4* peritectic Ti2 0 o 4* heta-Ti2 Co eutectic 1460158 5 TiCo + peritectic Ti2 Co 4- heta—TigCo eutectic 1500159 5 TiCo 4* peritectic Ti Co 4- heta—Ti2 Go eutectic 1 5 2 0 1 7 2 3 TiCo 4- peritectic Ti2 0o 4- trace heta 15^0173 3 TiCo 4* small amount second phase (Ti2 Co) I55C171 5 Large grains TiCo 4* small particle of second phase 1570174 3 Essentially single phase (TiCo) 1 6 0 0 1 7 5 3 TiCo2 + TiOo 1640176 3 TiCo2 Ti Oo 1680177 5 TiCo2 4* TiOo 4* small particles of impurity or third phase 6o TABLE IV

Microstructures of Homogenized Alloys**

Alloy Vickers Hardness Designation after homog. *** Microstructure

I1G156A* 128 Very coarse acicular transformed—alpha I2C160A* 150 Very coarse acicular transformed— alpha 13 CD.61A* 166 Coarse acicular transformed—alpha l4ci62A* 186 Acicular transformed-alpha I50166A* 207 Acicular transformed—alpha I60167A* 243 Acicular transformed-alpha I7C165A 270 Acicular transformed-alpha I8G163A 314 Acicular transformed-alpha I9G170A 38 7 Homogeneous retained beta I10G168A 394 Homogeneous retained beta I120151A 351 Homogeneous retained beta I14C142A 348 Homogeneous retained beta I16C149A 366 Retained beta plus TigCo I180152A 373 Retained beta plus TigCo I20C153A. 413 Retained beta plus TigCo I220155A 417 Retained beta plus Tig Go I24C157A 413 Retained beta plus TigCo I26C128A 405 Retained beta plus TigCo I28C138A. 401 Retained beta plus TigCo I30C130A 473 Retained beta plus Tig Go I32C131A 488 Retained beta plus TigGo I34C132A — Retained beta plus Tig Co I360133A — Retained beta plus Tig Co 138015^-B 548 Retained beta plus TigGo I42C157A 542 Tig Go 4- TiCo I46C158A 455 TigCo 4- TiOo I50C159A 370 TigGo 4* TiOo I52C172A 3 0 6 Ti2 Co 4- TiCo I54C173A 243 TigCo 4* TiCo I550171A 185 TiOo plus small amount of a second phase I57C172+A 319 Essentially single phase (TIGo) I600175A. 530 TiCo 4- TiCo2 1640176a 620 TiCo 4- TiCog I68C177A 715 TiCo 4- TiCog * Alloys 1 — 6n cold compressed 55»52,50»47,19»4$ respectively prior to homogenization. ** Alloys 1-9^ heated at 1025°C.* remainder at 930°C. All alloys heated for 72 hours except I38C154B for 96 hours and 60,64,68$ for 168 hours. *** 10 Kgm. load; 2/3B objective. 61

TABLE V

Microstructures of Alloys Equilibrated for Beta (Alpha 4- Beta) Solvus

Specimen Thermal Treatment* Designation Temp. (°C) Time (hrs.) Microstructure

I1G156B 850 72 20$ alpha 4- 80$ transformed alpha I2C160C 850 72 100$ transformed alpha 1301610 850 72 100$ transformed alpha

I20160B 800 168 60$ alpha + h0$ transformed alpha I3C161B 800 168 40$ alpha + 6 0 $ transformed alpha I^Cl62B 800 168 20$ alpha + 8 0$ transformed alpha I5C166B 800 168 5$ alpha -t* 95$ transformed alpha

1^01620 750 267 60$ alpha 4* 40$ transformed alpha 1501660 750 267 *K)$ alpha + 60$ transformed alpha 16016TB 750 267 20$ alpha + 8 0 $ transformed alpha I7C165B 750 267 100$ retained heta I80163D 750 267 100$ retained heta

1601670 700 360 35$ alpha + 6 5 $ retained heta 1701650 700 360 20$ alpha *f* 80$ retained heta I8C163B 700 360 10$ alpha + 90$ retained heta I9C170B 700 216 90$ retained heta; balance possibly alpha and Ti2 0 o

X8C163E 675 56^ Possibly alpha + heta + T±2 Co

I801630 650 510 Probably eutectoid products of alpha plus Ti2 Co

* Alloys 1—6$ and specimen I8C163B cold compressed 75$ or until onset of cracking after homogenization and prior to equilibration. T&BLE VI 62 Microstructures of Specimens for Betermination. of Beta/ (Beta •+• TigGo) Solvus (initial Treatment: 72 hours at 930°C.) Specimen Thermal Treatment Designation Terap.(°C) Time (hrs.) Microstructure

I10C168B 1025 8 100$ retained "beta I12C3L51B 1025 8 100$ retained heta Il4Cl42D 1025 8 100$ retained heta i i 6ci49d 1025 8 100$ retained heta I180152H 1025 8 liquid plus solid I20C1530 1025 8 liquid plus solid

Il4Cl42E 1000 4 100$ retained heta Il6Cl49E 1000 4 100$ retained heta I18C152I 1000 4 retained heta plus very small TigCo I20C153B 1000 4 retained heta plus small amt. Ti2 Co

214C142F 975 9 100$ retained heta 11601493* 975 9 retained beta+very small amt.TigCo I18C152J 975 9 retained heta 4> small amount TigCo

11001680 930 12 100$ retained heta 1120151c 930 12 100$ retained heta Il4Cl42C 930 12 retained beta-fyery small amt.TigCo 11601490 930 12 retained heta ■+■ small amount TigCo

I10G168D 900 24 100$ retained heta 1120151U 900 24 100$ retained heta Il4Cl42H 900 24 retained heta + small amount TigGo

I100168E 850 48 100$ retained heta I12G151E 850 48 retained beta+very small amt. TigCo 11401421 850 48 retained heta + small amt. TigCo

11001683* 800 168 100$ retained heta 11201513* 800 168 retained heta + small amt. Ti2 Co

I10C168G 750 280 100$ retained heta I12C1510 750 280 retained heta + small amt. TigCo

I90170B 700 216 possibly heta + alpha + TigCo 110 C168H 700 360 retained heta+very small amt.TigCo I12C151H 700 360 retained beta+small amount TigCo

I90170B 675 216 prohahly eutectoid products alpha+TigCo I10C168I 675 564 possibly heta + alpha TigCo I12C151I 675 564 possibly heta + alpha + TigCo 63 TABLE VII

Determination of Beta — TigCo Eutectic Horizontal

(Initial Treatment: 72 hours at 930°C.)

Specimen Designation Temperature (°0) Phases

I18C152G 1018 * IOO56 solid Cbeta+TigCo) I18C152C 1025 * solid 4- liquid I180152D 1054 solid 4* liquid 118 Cl52333 1071 solid 4- liquid I18C152F 1077 solid 4* liquid

I20C153B 1025 * solid 4- liquid

I22C155B 1032 solid 4- 1 5 liquid

I24C127C 996 * 1 0 0 $ solid I24C127D 1014 * 10056 solid I24C12?F 1043 solid 4- 15^ liquid

I26C128C 996 * 1 0 0 ^ solid I26C128D 1014 * 10056 solid I26C128F ioh-3 solid 4- 65$ liquid

I28C138C 996 tie IOO56 solid I28C138D 1014 * 10056 solia I28C13BG 1027 solid 4* 60$ liquid I28C138F 10A3 solid 4- 9756 liquid

1300130C 996 * IOO56 solid I30C130D 10l4 * 10056 solid I30C130G 1043 solid 4- 80$ liquid I30C130F 1055 solid 4- 90^ liquid

I32C131C 996 »Ss 10056 solid I32C13H> ioi4 Jit 100$ solid

All specimens marked with asterisk were examined metallograph!cally for evidence of melting. Balance of specimens examined visually and extent of melting estimated from amount of original specimen unaffected hy treatment. SA3LB VIII

Determination, of Tl2 Co—TiCo Peritectic Temp e rat'are* (initial Treatment: 72 hours at 930°C)

Specimen'Designation Temperature (°0) Phases

I^2C152B 1 0 2 5 100$ solid 1^201520 1050 100$ solid I^2C152D 10 8o solid + liquid

I46C158B 1 0 2 5 100$ solid 1^6 Cl 58 C 1060 solid i* liquid I4-6C158D 1113 solid + liquid

I500159B 1025 100$ solid 150Cl59C 1050 100$ solid I50C159D 1113 solid + liquid

* All specimens examined metallographically- for evidence of melting. Degree of melting was sufficiently- limited to make estimation "by visual examination unreliable. 65

TABLE IX

X—Bay Diffraction Data for Specimen I8 CI6 3 E

(Homogenized 72 hours at 1025°0; equilibrated 564- hours at 675°C

This Investigation* Alpha—Ti** Beta—Ti***

a (A) I/Io a i / i 0 8-0 hkl 2.553 4- 2-54- 3 2.284- 10 2.23 10 3.22 110 2.026 4- 1.822 2 1.626 2 3.25 200 1.4-79 2 1.4-7 1 1-319 3 1.33 1 3.22 211 1 .266 1 1.2 7 5 0.1 I.O8 7 4- 0.980 8 0.9564- 3 0.9109 1

* Mojg radiation.

** ASTM X—Hay Diffraction Data, First Supplement.

*** Calculated for three strongest reflections. PAGE 66, TABLE X , LACKING. FILMED AS RECEIVED FROM THE OHIO STATE UNI- YMiSXTY,

UNIVERSITY MICROFILMS, INC TABLE XI

X-Ray Diffraction Data for Ti Co (Specimen I3S0154A)

(Homogenized 48 hours at 930°C)

Tiiis Investigation ; Dawez Taylor^^) S. H H d(A) 0 hkl d(dK) X4» 6.4o 7 4 111 6.53 w — — 220 3.97 vw 3.226 3 222 3.26 w —— 400 2.83 vw 2.579 4 331 2.59 w 2.295 6 422 2.31 m 333- 2.167 10 511 2.17 s 1.988 6 440 2.00 m 1.903 3 531 1.91 vw 1.877 4 442 1.88 w — 622 — 1.629 1 444 1.63 w 711- 1.580 2 551 1.59 w 1-507 1 642 1-51 w 731“ 1.468 4 553 1.472 w l.4i2 1 800 1.413 vw 1.380 1 733 1.382 w 822- 1.330 8 660 1.33h m 1.304 4 555 1.305 w 1.136 6 755 1.136 m 0.94x5 6 12,00 0 .9423 m 0.9318 6 777 0.9330 m 0 .9164 6 1 2, 2 2 0 . 9 1 7 2 m

* These data should also- he compared with “d 11 spacings for the cohalt-poor TiCog phase of Wallhaum (Tahle XIV) since Eoatoker^^ suggests that pattern for true Ti2 Co phase would he similar. 68

TABLE XII

X-Eay Diffraction Data for Specimen I52C172A

(Homogenized 72 Honrs at 930°C)

This Investigation* TiCo d(i) I/I d(dX) I hkl « 2.296 3 2.31 m 2.169 5 2.17 s 2.110 10 - 110 2. 98 2.018 4 - 1.994 4 2.00 m 1.496 2 200 2. 99 1.331 2 1.334 m 1.223 8 - 211 2. 99 1.171 1 - 1.133 1 1.136 m 1.111 1 1.109 vw 1.059 2 220 j .00

* Cobalt K—alpha radiation 69

TABLE XIII

X—Bay Diffraction Results for Specimen I68C177A.

bid a(£) x/l ao 111 3.8ifif 5 6.65 Ti C02 220 2.36if 7 6.68 TiCo2 ( n o 2-097 8 2.97) TiCo 311 2.018 10 6.69 TiCo2 222 1.932 8 6.69 TiCo2 boo 1.67^ Ur 6.69 TiCo2 531 1.558 2 6.80 TiCo2 (200 l.if85 3 2.97) TiCo ^ 22 1.368 5 6.70 TiCo2 333 1.290 8 6.71 TiCo2 (211 1.212 5 2.97) TiCo2 *440 1.185 8 6.70 TiCo2 531 1.133 2 6.71 TiCo2 630 1.061 3 6.71 TiCo2 (220 1.050 3 2.97) TiCo 533 1.023 8 6.71 TiCo 2 622 1.011 8 6.71 TiCo2 U-UU- 0.968 1 6.71 TiCo2 (310 0.939 Ur 2.97) TiCo 70 TAJBIiE XIV

Interplanar Spacings o f TiCog Prom tlie Literature

Duwez and Taylor Wallbaum and Witte^*^ hKl d(kac) I hXl a (lex) I 100 4 . 0 8 w 111 ; 3.99 w 101 3-93 VW 220 2.37 m 004 3-85 w 311 2.02 s 102 3.63 tv 222 1.93 m 105 2 .4 i vw 400 1.67 m 110 2.36 w 311 1.535 w 106 2.17 m 422 1.363 m 201 -1 1 4 2.02 s 333 1.284 s 202 1.98 m 44o 1.188 m 107-108 1.93 m (plus 2 .08m and 1.200m 203 1.90 w attributed to the pressure 204 1.80 w of TiCo) 108 - 205 1-71 vw 206 - 211 1.53 vw 213 1.48 w 214 1.42 vw 300 1.362 vw 10,11-216 1.325 w 209 1.308 w 304-00.12 1.280 w 217 1.263 vw 20,10 1.229 vw 220 1.181 m iFigSxare 1

-A-x*e Melting Furnace arc welder (-)

H20 Sight glass hot cold To vacuum pump a

y -

/ Hg manometer

Copper crucible Legend for Figure 3

Accessories for Arc-Melting Fhraflce

A. Spun Copper Crucible t B. Tungsten Electrode Tip

0. Copper Insert or Melting Earth.

D. Ten-Cram Button (as cut prior to third and fourth meltings)

E. Five-Cram Button

F. Fixture for Cutting Slabs from Cast Buttons Figure 3

Accessories for Arc-Melting Furnace Legend for Figure k-

Arrangement of Apparatus for Sealing

Specimens in Capsules

A. Mechanical Fore Pump

B. Three-Stage Oil Diffusion Pump

G. Ionization Gage Tube

D. Ionization Gage

E. Insert Gas Inlet

F. Air Inlet

G. Mercui’y Manometer

H. Pyrex-to—Vycor Graded Seal

I. Capsules A ARRANGEMENT OF APPARATUS FOR SEALING SPECIMENS

F ig. 4 77

Figure 5

High. Temperature Resistance Furnace Legend for Figure 6

Circuit Diagram for High—Temperature

Resistance Furnace

A. 220-volt, 3-wire Single Phase Line

B. Triple—Pole, Single—Throw* Fused Switch.

C. 115-volt Pilot Light

D. 220—volt, 5*85 KVA Autotransformer

E. 220-volt, 5 KVA, 10:1 Transformer

F. 600/5—1amperes Current Transformer

(K Furnace Element

H. Double—Pole, Double—Throw Toggle Switch

I. Single—Pole, Single-Throw, Hold-In Switch

J. 0—300 AC Voltmeter

K. 0—25 AC Ammeter

L. 0—100 AC Ammeter

M. 0-10 AC Voltmeter

H. 0— 5 AC Voltmeter A 0 H JK B ® ' 0 0 O Q a

o-

D

f ^ — 6

a-

F u m i /

rm x

-o CIRCUIT DIAGRAM FOR HIGH “•TEMPERATURE FURNACE *«4 S> F ig. 4 80

Figure 7

Equipment for Resistivity Measurements 81

Legend for Figure 8

Electrical Circuit for Resistivity Measurements

A. 15— ohm Variable Resistor

B. 125~ohm Variable Resistor

C. 1000—ohm Variable Resistor

D. 0— 10 B.C. Ammeter

E. Standard Resistance (5 Anrpere, $0 Millivolt Shunt)

F. Double-Pole, Double—Throw Knife Switch

G-. Four-Pole, Double—Throw Knife Switch

H. Double-Pole, Double-Throw Knife Switch

J. 6—Volt Wet Cell Storage Battery

K. Leads to Tungar Battery Charger

L. Leads to Potentiometer

M. Current Leads to Specimen

H. Voltage Leads to Specimen riO 1_____i

LkD h Oh rfo f) O h

ELECTRICAL CIRCUIT FOR RESISTIVITY MEASUREMENTS

Fig. Q > 83 Microstructures of As-Cast Alloys

Figure 9 • 2$Co Figure 10 55&C o 375X aq.. HF-HNOo 375X aq.HF-HN(>3 Coarse, acicular structure Acicular, transformed alpha. of alpha transformed from Former "beta grain "boundary- beta on cooling faint ly visible.

Figure 11 9%0o Figure 12 22$Co 65X aq_.HF 595X HF-HgOg

Dendritic coring in retained Primary "beta ("black) plus "beta. eutectic mixture of "beta and gamma (compound)

Figure 13 Z6%Go Figure 1^ 28$Co 250X glyc. HF-HNO^ 250X glye.HF-HNC^

Primary dendrites of "beta Nearly 100$ eutectic mixture (light) in eutectic matrix of "beta plus gamma, of "beta plus gamma. £&•

V > M , / - _vV • .. yj*-' ’ - V"* ;i'- i '.V^'/C

u ' - r ' 85 Mi cro struct lire s of As— Cast Alloys

Figure 15 ,32$Co Figure 16 ,3^$Co 250X glyc. HF-HCTO^ 3 75X glyc, HF—HMOrj

Primary dendrites of gamma Primary dendrites of gamma (Ti2 Co) in eutectic mixture in eutectic mixture of beta of beta plus gamma. (Small plus gamma. The dendritic ’•dots** represent impurities). gamma forms a peritectic reaction rim around non- equilibrium delta (TiCo)

Figure 17 38^Co Figure 18 38$Co 70X HF-H2 02 1200X HF-H2 02

Dendrites of gamma plus non­ Same micro structure as pro­ equilibrium delta in matrix ceeding Figure showing reso­ of eutectic beta—plus-gamma lution of eutectic mixture: beta (dark) plus TigCo-

Figure 19 A 6 ^Co Figure 20 5ZfoGo 595X HF-H2 02 595X HF-H2 02

Iiarge dendritic areas of TiCo Same microstructure as pre- surrounded by peritectic Ti2Co ceeding Figure showing and non-equilibrium eutectic increased amount of primary mixture of beta (dark) plus TiCo and vestiges of non- Ti2Co equilibrium eutectic.

8 7 Microstructures of As-Cast Alloys

Figure 21 55$Co 130X hf-h2o2

Large, columnar grains of TiGo (slightly cored) plus trace of second phase (small "black areas).

Figure 22 68$Co 375X 25j6K2Sofr

Mixture of TiCo and TiCo2 plus small dendrite (hlack) of impurity or high-melting third phase. 88

4 '^,*£w$rt^- v I m m k .

Fij. 22 89 Microstructures of Homogenized Alloys

(2,5*9$ cobalt alloys homogenized 72 hours at 1025°C; remainder treated at 930° C. for 72 hours)

Figure 23 2$Co Figure 2h 5$Co 65X aq..HF 65X aq..HF

Coarse, acicular transformed- Acicular transformed alpha, alpha. Bote former heta Finer structure than in 2$ grain boundary. alloy.

Figure 25 9$Co Figure 26 l8 $Co 65X aq.. HF-HNO3 70X HF-H202

Coarse-grained, retained heta TigCo (light) in matrix of phase. (Black dots are etch- retained heta phase, ing pits).

Figure 27 2*f$Co Figure 28 26$Co 70X HF-HgOg 70X HF-HgOg

TigCo (light) in matrix TigCo (light) in matrix of of retained is eta phase retained heta phase.

91 Mierostructuree of .Homogenized Alloys (Heat treated for 72 Hours at 930°C)

Figure 29 28%0o Figure 30 30$Co TTtit tT A 70X h f -h 2o2 70X rUJ —**2 2 Ti2Co (light) in matrix Ti Go (light) plus retained of retained "beta phase he€a phase.

Figure 31 32^C< Figure 32 38$Co 70X h f -h 2o 2 70X HF-HgOg

TigCo (light) plus retained Small particles of retained heta phase. heta phase surrounded hy 9?i2Co. (Homogenized 96 hours at 930°C.).

Figure 33 W C o Figure 3k 55%Co 70X HF—HgOg 375X aq.HF

Dendrites of 2iCo in matrix Small particles of second of TigCo. phase - prohahly TigCo - in matrix of TiCo. 1

Pij.Zi

* \ ,, V W ^ '-a ' ' . o-n -<*■ t V• t * •■■' ■'.■• ■ . T>-* * „r. ^0 i-x■'Op ,k s _/l., *,v Vv V f a ’ »• £ •-> v **%•* • c** -Vv D. t- .»•* ■'¥. : * . • » j • ' s '7 «■*"?A / ■ .£4*:i?-' *v -A

-t'•-f. ■ - *•• ^4 4 „ */*>.. *c<*. -*%*.* • J» **’ V* ^•> vy ‘ 1- V >v>.- ^5 * V " . - v.' * * ‘ > . * > * v ■ ■ ^ - . ^ '. >1 • - ‘ ' -i-^-. \ j_u&* • •• • ,.‘4• \t • ■-„ v ' V>". ;V V '*; , ,* » V *..; f'* ~ ' * ~: ■’ '■ ■■■'.1 f^ 1. V “ »L-:- “-i " > '• 7 -. ' '-. r’ vi »“ ' - '• ' — • •' ' ■ » • r V- *■ * ✓V V ' • S ' # ' & - * <» '‘J-

/=/^33 31/- Microstructures of Homogenized Allova (Heat treated for 168 hours at 930°G)

Figure 35 68$Co 37SX aq..HF

TiCo (dark) plus TiCog 9b

.-.-j-SasiQ

F.$. 35 (Typical Micro structures in Determination, of Solubility Limits

Figure 36 6<$> Co Figure 37 8$Co 65X aq.HF 65X aq. HF

Homogenized 72 hours at 1025° C. , Same treatment as Figure 36 wat er—quencheds equilibrated 360 hours at 700° C.

Equilibrium alpha (light) in Equilibrium alpha (light) matrix of retained beta. in matrix of retained beta.

Figure 38 12^Co 65X HF-h 202

Homogenized 72 hours 930°C., wat er—quenched; equilibrat ed 8 hours at 1025°C., water- quenched; equilibrated 360 hours at 700°C., water- quenched.

(TigCo (Light) in matrix of retained beta phase. 96

P,'j. 3% Micro at ru.etures Showing Eutectoid Decomposition

(Oast- alloys homogenized for .72 hours at 1025°C)

Figure 39 QfoGo 120OX • aq.HF

Equilibrated 510 hours at 650°C.

Probably 2i2Co (small particle) in matrix of alpha-Ti

Figure 9$0o Figure 4l 9$Co 65X HF-H202 ’ 1200X HF-K2O2

Equi 1 ibrat ed 216 hours at 675°C.

Ti2 Co in matrix of alpha-Ti 98

FiS • 3 9 MetalIogra-phic Evidence of Melting

Figure H-Z 18^Co 595X h f -h 2o2

Specimen heated at 1025°C. for one hour.

Black field represents unaffected “beta grains. White rimmed portion of field is an area formerly Ti2Co at the beta grain boundaries. Melting has converted the Ii2Co grains to a eutectic mixture of beta phase and Ti20o.

Figure k-J 46/oCo 375X B M g O g

Specimen heated to lo6o°C.

Large white grains are TiCo. Grain boundary area represents non-equilib­ rium beta phase (black) and Si2Co from liquid phase. o

100

?;$• 4 3 101 Microstracturee of Specimens Showing Probable Pay gen and/or Nitrogen Contamination (Alloys homogenised 1025° C» for 72 hours)

Figure 44 8$Go 65X HF-H202

Equilibrated 564 hours at 675° C.

Figure 45 9$>Go 260X aq_. HF-Ht'TO^

Equilibrated 216 hours at 700°0.

Figure 46 lO^Go 375X HF-H202

Equilibrated 564 hours at 675° 0.

All three figures probably show alpha phase and Ti2Co

All three figures probably show alpha phase and Ti2Co precipitated in a matrix of beta phase. 102

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■ F > j. -4 U / 0 3

XSo. <-

S.

J

U C o b a lt /

V f It Percen Wc/y Wc/y

•o

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9-r*S~-'9

/

u..<**■ o i-"

X V o

>- \3 fcf ■ ' f c * 2

& I 0 /— <3 Q \s 2 ..1 C „J <» Ck ■o P •5; ■'H V-> ■>J- w «0 *> X: «5 ■ £ ■ X «0 >u 05 "-c vu v> s: ftU Q

c £ \•%. o \ ^ vi: - < % >u i

JL o < 3 o O o Cs o Q ■Ck o £ VS , «V 106

literature cited

1, J.R. Long, E.T. Hayes, D.C. Root, and C.E. Armantrout, "A Tentative Titanium—Nickel Diagram.H U.S. Bur. Mines. Rpt. Inv. Ho. 4463, Feb. *49, 13 PP.

2. Howard C. Gross, H Titanium-Base Alloys.” Ren ort of Symnoalm on Titanium. Office of Naval, Research., U.S. Navy. March 194-9. p.125-131.

3* R.I. Jaffee, D.J. Mayfcuth, Bruce W. Gonser, "Titanium-Base Alloys. Prepared hy Powder Metallurgy Methods.” U.S. Air Force Project RAND Report No. R-131. March 15, 1949* p.79.

4. W.E. Kuhn, H.V. Kinsey, and 0.¥. Ellis, nA Study of Some Alloys of Titanium in the Manufacture of Which Commercial Titanium Hydride Powder Was Used,” Trans. Can. Inst. Min. & Met. vol. 53, 1950, p.54-67.

5 . D.J. McPherson and M.G. Fontana, ”Properties of Melted and Forged Titanium-Chromium Alloys." Metal Progress. 55 (March 1949)i PP. 366-7.

6. • P.H. Brac.el W.J. Hurford, and T.H. Gray, "Preparation and Prop­ erties of Titanium—Base Alloys." Ind. & Eng. Chem. . v.42, Feb. 195Q, p.227-236.

7. J.B. Sutton and T.D. McKinley, "Induction Melting of Titanium in Graphite." Met. Frog.. 55, 3Feb. , 1949, pp.195*

8. E.A. Gee, J.B. Sutton, and W.J. Barth, "Effect of Carbon in Titanium Metal Ingots," Ind. & Eng. Chem. v. 42, Feb. 1950, p.243-249.

9. W.E. Kuhn, "Production-of Titanium Ingots by Melting Sponge Metal in Small Inert-Atmosphere Arc Furnaces." Paper presented before the April 1951 meeting of the American Electrochemical Society.

10. W. von Bolten, Z. Elektrochem. 11, 45, 1905-

11.. R.W. Moore, "Preparation of Metallic Uranium." Trans. Eiectro- chem Soc. 43, 1923, p.317-323.

12. R.M. Parke and J.I#. Ham. "The Melting of Molybdenum in the Vacuum Arc." Metals Tech. T.F. #2052, 13, 6, Sept. 1946.

13« W. Kroll, "The Production of Ductile Titanium." Trans. Electro- Chem. Soc.. ?8, 1940, pp.35-4?. 107

14. O.W. Simmons, C.T. G-reenidge, and L.W. Eastwood, "Arc Melting of Titanium." Met. Prog. 55* Peb. 1949, pp.197-200.

15. D.J. McPherson. "The Preparation and Properties of Titanium- Chromium Binary Alloys." Ph.D. Dissertation. The Ohio State University, June 1949.

1 6 . Earl A. Gulbransen and Kenneth P. Andrew, "Kinetics of the Reac­ tions of Titanium with O2 , Ho and Hg.” Trans. AIMS, v.185* P*?4l, 1949.

17. Robert I. Jaffee and I.E. Campbell, "The Effect of Oxygen, Nitrogen and Hydrogen on Iodide Refined Titanium," Trans.AIMS. v. 185, 1949, p . 646.

18. M.H. Davies and C.E. Birehmall, "Oxidation of Titanium•11 Jnl. Metals. October 1951* pp.877-880.

19. E.S. Bumps:, H.D. Kessler, and M. Hansen, "The Titanium-Oxygen System." Trans. AS M , w.45, 1952, p.1008. 2 0 . R.I. Jaffee, H.R. Ogden, and D.J. Mayfcuth, "Alloys of Titanium with Carbon, Oxygen and Nitrogen." Trans. AIME. v«188,1950, p•I2 6 1 .

2 1 . Peter H« Morton, W.M. Baldwin, Jr. "The Sealing of Titanium in Air." Trans. A.S.M.. v.44, 1952, p.1004.

22. Prank B. Cuff, et al* "The Titanium-Copper Alloy System." AP Technical Renort No. 6595. Part I. Wright Air Development Center, Wright—Patterson Ain Force Base, November 1951•

23. D.J. Mayknth, H.R. Ogden, and R.I~ Jaffee, "The Titanium—Mangan­ ese System," Jnl. Metals, v.5* No. 2, Sect.2, Pebruary 1953* p.225.

24. M. Hansen, E.L. Kamen, H.D. Kessler, and D.J. McPherson, "The Systems Titanium-Molybdenum and Titanium-Columbium, " Jnl .Metal s. v.3» October 1951* p.881-888.

25. M. Hansen, H.D. Kessler, and D.J. McPherson, "The Titanium— Silicon System." Trans. ASM, v.44, 1952, p.520.

2 6 . H. Margolin, Elmars Ence, and J.P. Nielsen, "The Titanium-Niekel Phase Diagram." Jnl . Metals, v.5* No. 2, Sect. 2, Pebruary 1953* p .243 .

27. C.E. Lundin, D.J. McPherson, and M. Hansen, "The System Zirconium- Copper." Jnl . Metals, v.5* No.2, Sect. 2, Pebruary 1953* p.2?3- 108

28. D.J. Maykuth, H.R. Ogden, and R. I. Jaffee, "The Titanium-Tungsten and Titanium—Tantalum System. ,r Jnl. Metals, v.5* Ho.2, Sect. 2, Peb. 1953. p-231.

29. R.P. Domagala, D.J. McPherson, and M. Hansen, "The System Zir­ conium-Chromiixm, " Jnl. Metals, v.5, Ho.2, Sect. 2, Pebruary 1953, p.279.

30. R. J. Van Thyne, H.D. Kessler, and M. Hansen, "The Systems titan­ ium-Chromium and Titanium-Iron," Trans ASM, v.44, 1952, p.974.

31- Irving Cadoff and J.P. Hielsen, "The System Titanium-Carbon." Jnl. Metals, v.5* Ho.2, Sect.2, Pebruary 1953* p.248.

32. C. G. Wang, H.J. Grant, and C.P. Ploe, "The Titanium Rich Titan­ ium-Chromium-Oxygen System. H Wright Air Development Center Technical Report #52— 255* Hovember 1952.

33. P.H. McRitehie and H.H. Ault," "Design of High-Temperature Re­ sistance Pomace," Jnl. Am.Cer.Soc. v.33, Ho.l, p.25-

34. W.E. Pew and G.K. Manning, HA 4000° Purnace," Metal Progress, March, 1951, v.5 9 , p.364.

35. W.J. Pretague, C.S. Barker, P.A. Peretti, "The Titanium-Iron Phase Diagram." Wright Air Development Center Technical Report Ho. 6597, Part 2 (March 1952).

3^. U.S. Department of Commerce, "Tables for Conversion of X-Ray Diffraction Angles to Interplanar Spacing. " national Bureau of Standards Applied Mathematics Series—10. (1950).

37- H.P. Roth, "Microstructxxre of Titanium,” Met. Prog. , v.59, June, 1951, p .8l6B.

38. Pierre A. Jacquet, "Electrolytic Oxidation and Polishing of Titan­ ium and Their Application in Investigation of Microstructures,” Comptes Rendus, v.232, Jan. 3* 1951* p.71—73*

39. D.A. Sutcliffe, J.I.M. Porsyth, and J.A. Reynolds, "Electrolytic Polishing of Titanium," Metallurgia, v.4l, Mar. 1950, p. 283-284.

40. Pierre A. Jacquet, "The Safe Use of Perchloric-Acetic Electropol­ ishing Baths,” Metal Finishing, v.47, Ho.1949, p.62-69-

41. "Titanium Metallography — Simple* Safe,” Iron Age, v.170, Aug. 28, 1952, p.112.

42. Constance B. Craver, "Differentiation of Grain Size and Phases in Titanium," Metal Prog., v.59» Mar., 1951* p-371“373* 109

43- R.K. McGeary, J.K. Stanley, and T.D. Yensen, "Determination of Oxygen in Metals "by the Vacuum Fusion Method,11 Am. Soc. Met., Preprint No. 10, 1949, 16 pages.

44. Gerhard Derge, “Analysis of Oxygen in Titanium,11 Jnl. of Metals, 1 (Oct. 1949), pp.31~3*

4-5* G. Grube, “On the Electrical Conductivity of Binary Alloys,H Zeit. f. Electrochemic, v. 54 (March 1950), pp.99-107*

46. Bruce W. Gonser, "Titanium Alloys," Ind. & Eng. Chem., v.42, Feb., 1950, p.222-226.

47- W. Rostoker and H.i). Kessler, "Titanium Alloy Development Mapped, " Iron Age, v.169, June 19, 1952, p.136-142.

48. Wilhelm Kroll, "Deformable Alloys of Titanium. " Z. Metallkunde, 22 (1937), pp.189-192.

49. E.I. Larsen, E.F. .Swazy, L. S. Busch, R.H. Freyer, ^Properties of Binary Sintered and Boiled Titanium Alloys," Metals Progress, 55 (March, 1949) » "pp.359-61.

50. O.M. Craighead, O.VT. Simmons, and L .W . Eastwood, "Titanium Binary Alloys," Trans. AIME, v„l8 8 , Mar., 1950, p.485-513.

51. A-D. McQuillan, "Allotropic Transformations in Titanium," Nature, 164 (July 3. 1949), pp.24.

52. A.D. McQuillan, "An Experimental and Thermodynamic Investigation of the Hydrogen-Titanium System," Royal Society, ser. A, v.204, Dec.22, 1950, p.309-323. .

53* A.D. McQuillan, "The Titanium-Hydrogen System for Magnesium— Reduced Titanium," Jnl. Inst. Metals, v.79, July 1951, p-371-378.

54. A.D. McQuillan, "The Application of Hydrogen Equilibrium—Pressure Measurements to the Investigation of Titanium Alloys Systems," Jnl. Inst. Metals, v.79, Apr. 1951, p«73”88.

55. A.D. McQuillan, "The Effect of the Elements of the First Long Period on the Alpha-Beta Transformation in Titanium," J. Inst. Metals, (March 1952), v.80, no.7, pp.363—8 .

56. Nichi Hashimoto, "Relation Between the Allotropic Transformation of Cobalt and Some Additional Elements, " Met. Abs., 5 (1938), p.462, (Nippon Kinzokeo Gakkai-Si) , 1 (1937) pp.177—190.

57- Max Hansen, "Per Aufbau der Zweistofflegierungen," Julius Springer, Berlin, 1936, p.515- llo 58. f e m e r Koster and Ewald Wagner, "The Influence of the Elements Al, Ti, V, Cu, An, Sn and Sb on the Polymorphic Transformation of Cobalt," 2. Metallkunde, 29 (1937) » pp.203-232.

59- Werner Koster, "The System Iron— Cobalt—Titanium," Arch. Eisen- huttenwesen, 8 (1934— 5), pp.471—2.

o O . P. Lawes and H.J. Wallbaum, "The Crystal Chemistry of Titanium Alloys," Uaturwissenschaften 27 (1939) » pp.674-5.

61 . Han Joachim Wallbaum and Helmut Witte, "Crystal Structure of TiCo2H Z. Metallkxmde, 31 (1939), 6, pp.185-7-

62. H.J. Wallbaum, "The Systems of Iron— G-roup Metals \-7ith Ti, Zi, Cb, Ta,” Arch. Eisenhuttenw, 14 (1941), p.521.

63- Pol Duwez and Jack L. Taylor, "The Structure of Intermediate Phases" in Alloys of Titanium with Iron, Cobalt and Hickel," Trans. AIMS, v.188, 1950, p. 1173-1176.

64. H. Karlsson, "An X—Hay Study of the Phases in the Copper Titanium System,” Jnl. Inst. Metals, (1951). v.79, p.391.

65* IF. Karlsson, "Metallic Oxides with the Structure of High— Speed Steel Carbide," Hature, (Sept. 29, 1951), v.l68, p . 558.

66. W. Rostoker, "Observations on the Occurrence of T12X Phases," Trans.- AIME, v.194, 1952, p.209-210.

67. "Metals Handbook," American Society for Metals, Cleveland (1948) pp. 578-581.

68. Private Communication, J.B. Johnson, Wright Air Development Command to M.G-. Fontana, Ohio State University, October 11, 1949-

69- Walter L. Finlay and John A. Snyder, "Effects of Three Interstitial Solutes (Hitrogen, Oxygen, and Carbon) on the Mechanical Properties of High-Purity Alpha Titanium," Trans. AIME, v.188, Feb. 1950, p . 277-286.

70. Robert I. Jaffee and I.E. Campbell, "The Effect of Qaygen, nitro­ gen and Hydrogen on Iodide Befined Titanium," Trans. AIME, 8 5 (1949), pp.646— 654.

71- S.A. Herres and J.A. Davis,- "Arc—Melting Refractory Metals," Steel. 124 (May 2, 1949), pp.82-6, 135.

72. H. Vosskuhler, "Determining the Constitution of Metal Systems in the Solid State by Measuring Their Electrical Resistances," Metall. , v.4, June 1950, p.231-235- Ill

73- Pol Duwez and J.L. Taylor, "A Partial Titanium-Chr omiurn Phase Diagram," Trans* ASM, 1952, pp.^95-517*

7^. S* Jonkainen Arnold and Prank B. Cuff, "Studies and Experi­ mental Investigations for the Development of Phase Diagrams of the Titanium-Chr omium and Titaninm-Oopper Alloy Systems,” Wright Air Development Center. AF Technical Deport 6595* Part 2, December 1951•

75• Pol Duwez, "Effect of Hate of Cooling on the Alpha-Beta Trans­ formation in Titanium and Titanium-Molybdenum Alloys,” Trans. AIMS, t .191 (1951), p p .765-771.

76. Daniel S. Eppelsheimer and Hubert H. Penman, ’’Accurate Deter­ mination of the Lattice of Beta-Titanium at 900°,” Sature. v.l66, Dec. 2, 1950, p.960.

77. A.D. McQuillan, "Some Observations on the Transformation in Titanium,” Journal of the Institute of Metals, v.78, No.1950, p.2^9-257.

7 8 . E.S. Greiner and W.G._ Ellis, ”Thermal and Electrical Proper­ ties of Ductile Titanium,” Metals Technol. 15 (Sept. 19**-8) T„P. 2^66, 9 PP. Trans. AIME. (19^9) PP.657-665.

79. D.J. McPherson and M.G. Fontana, ’’Preparation and Properties of Titanium-Chromium Binary Alloys," Trans. A S M , v.^3 (l95l) * pp.1098-1125. 112

AUT OBI OGBAPHY

I, Frank Lewis Orrell, Jr., was: born in Lowell, Massa­ chusetts, December 27, 1916. 1 received my secondary school educa­ tion in the public schools of the city of Lowell, Massachusetts.

My undergraduate training was obtained at The Massachusetts Insti­ tute of Technology, from which I received the degree Bachelor of

Science in 1939, After approximately seven years industrial exper­ ience as a metallurgist, I enrolled in the graduate school of the

University of Kentucky, receiving the degree Master of Science in

Metallurgical Engineering in 19^7. Following graduation, I served for two years as Assistant Professor of Metallurgical Engineering at the University of Kentucky. In 19^9 I was awarded The Titanium

Alloy Manufacturing Division of the National Lead Company Graduate

Fellowship at The Ohio State University. I held this fellowship for two years of the time spent completing the requirements for the degree Doctor of Philosophy.