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5-8-1936 The onC trol of the Grain Size of Oswald J. Wick

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Recommended Citation Wick, Oswald J., "The onC trol of the Grain Size of Zinc" (1936). Bachelors Theses and Reports, 1928 - 1970. 67. http://digitalcommons.mtech.edu/bach_theses/67

This Bachelors Thesis is brought to you for free and open access by the Student Scholarship at Digital Commons @ Montana Tech. It has been accepted for inclusion in Bachelors Theses and Reports, 1928 - 1970 by an authorized administrator of Digital Commons @ Montana Tech. For more information, please contact [email protected]. I Wick,O.J.

THE CONTROL OF THE

GRAIN SIZE OF ZINC

by OSWALD J. WICK

A ThesIs SubmItted to the Department of Metallurgy in partIal FulfIllment of the Requirement for the Degree of BaChelor of Science in Metallurgical Engineering

MONTANA SCHOOL OF MINES BUTTE, MONTANA MAY8, 1936

~NTANA sCHga~Of MJNf! UBIWlY. .. - .;..... THE CONTROL OF THE GRAIN SIZE OF ZINC

by OSWALD J. WICK

A T~esis Subm1 tted to the Dep,artment of Metallurgy in partial Fu1fillment of the Requirement for the Degree ot Bachelor of Scienc~ in Metallurgioal Engineering I /17A7 ,I MONTANA SCHOOL OF MINE~ LlBBAB~o . - -...... , MONTANA SCijOOL OF MINES BUTTE. MONT ANA MAY 5, 1936 I .... ---

TABLE -OF CONTENTS Intr06uction- •••••••••••••••••••••••••••••••. o •••• o 1

Zinc- Equilibrium Diagram ••••••••••••••• o 2

Zinc-Tellurium Equilibrium Diagram •••••••••••••• o 3 Experimentation •••••••••••••••••••••••••••••••••• 4 Diseussion ••••••••••••••••••••••••••••••••••••••• 6

Sumrna-ry'. • • • • •.• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• 7

Bibliography ••••••••••••••••••••••••••••••••••••• 8 Illustrations •••••••••••••••••••••••••••••••••••• Figure 1 Zn-Se Equilibrium Diagram •••••••• 2

Figure 2 Zn-Te Equilibrium Diagram •••••••o 3 THE CONTROL OF THE GRAIN SIZE OF ZINC

INTRODUCTION The use of zinc as a structural has been militated against by two of its properties, namely, its low tensile strength and its susceptibility to grain growth. The importance of these factors can be appreciated when it is realized that the tensile strength of coarsely crystalline cast zinc is 4,000 pounds per square inch (1) while finely crystalline cast zinc has a tensile strength of 12,000 pounds per square inch and since grain growth in zinc proceeds at room temperatures (2), all zinc regardless of its initial state loses strength until it reaches the value of the coarsely crystalline variety. The effect of the elements tellurium and selenium were selected for study. Tellurium was selected because of the remarkable effect it has on the grain size of (3). Selenium was eltminated as a possibility when it was found that it is completely insoluble in zinc in both the liquid and states as shown by the equilibrium diagram (Figure 1). The zinc-tellurium equilibrium diagram is shown in Figure 2. Concerning the diagram Mellor (4) states: "M. Kobayashi found that alloys of tellurium and zinc furnish a freezing point curve which shows the ex1stance (l) Hayward, Outlines of Metallurgical Practice, pp 234 (2) Liddell & Doan, Principles of Metallurgy, pp 547. (3) Peretti, Alloys of Lead and Tellurium (4) Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chemistry, Vol. XI, pp 50. ..

01 o o 0 0 0 0 0 0 o o

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t'-' 0 t-;g ..... (JQ ~ CD ():1 .... 0 ~ .....t'l l:$ CJ) a CD .p.- I .... 0 r:J') CD t'l (!) l:$ 1:1 ...... t-:3 CD :a I:l ~ t'l + 0 ..... • I:i .....t-I ~ ~01 ,. .0 t-I 0 p ..... t_:<:J 0' UJ 1-"- lQ .0 ~ (!) OJ P p ...... :ii UJ OJ .... (!) CD 02 ..... , ..... 0' (JQ 0\ '"..... g 0 ~ ...... t::1 P' -a f'Jl:? 0 Pi s:o B

co 0

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-3- -3-

I _---ZnTe 1238.5°0 11200 -

Liquid

1000 ,/ ,, .-, ,/ ZnTe +- Liquid ZnTe .- ,, + , Liquid 800 ,, I I I I I I ,I I I I 600 I I I I I I I I I I I 400

ZnTe+ Zn ZnTe +- Te

200

o o 10 20 30 40 50 Tellurium, % by weight Figure 2 Zinc-Tellurium Equilibrium Diagram -4-

of only one compound, ZnTe, with a maximum at 1238.5 O. The two eutectic points practically coincide with the melting points of the pure components. The freezing point curve falls steadily from the compound to tellurium, but alloys richer in zinc lose zinc so rapidly by volatil- ization that it is not possible to determine the course of the curve, although the zinc eutectic arrest is well marked." The indefiniteness of the diagram made it difficult to determine the various oonstituents of the alloys when examined under the microscope. EXPERIMENTATION The zinc used in making the alloys was Anaconda Electrolytic Zinc. The tellurium used was secured from the Raritan Works at Perth Ambqy, New Jersey.

\ The alloys studied were made by placing the required amo~ts of zinc and tellurium in a covered, graphite lined crucible and heating to the required temp- erature in a closed muffle. The charge was covered with powdered charcoal to prevent oxidation. When the alloys were fused they were removed from the furnace, stirred with a carbon rod, and east in carbon molds. By this method a 5% tellurium was made from which l%'and 1/10% tellurium alloys were made up. Attempts to make a "'. 50% tellurium alloy were unsuccessful because of the extreme volatility and rapid oxidation of the zinc at the -5-

high temperature required. pure zinc specimens for comparative purposes were also made under the same conditions

• as were the alloys • Different samples from each of tbe pure zinc, . 1% tellurium, and 1/10% tellurium castings were treated

-1 as follows: a. Cast metal

b. Cast metal annealed one hour at 200 C

J c. Cast metal rolled (R. A. 25%) d. Cast metal rolled (R. A. 25%) and annealed for one hour at 200 C e. Cast metal rolled to thin sheet f. Cast metal rolled to thin sheet and annealed for one hour at 200 c. The tellurium. alloys rolled easily at room temperatures. The pure zinc was rolled at a temperature between 100 and 150 C. The specimens were annealed in ceresine wax (ozokerite) maintained at 200 C for the required time. Specimens for microscopical examination were filed smooth and then successively ground on Hubert's No. 0, No. 00, No. 000, and No. 0000 abrasive paper. This was followed by polishing on a wheel with rouge, then levigated alumina, and finally on a felt covered -6-

N wheel with no added abrasive. Polished specimens were etched by dipping them in conoentrated nitric or by emmersing for about 2 seoonds in a solution containing 20 grams of chromic anhydride and 1.5 grams of anhydrous sodium sulphate in 100 ce of followed by a rinse

in a solution containing 200 grams H2Cr03 in a liter of water. Grain sizes were measured with a meohanical stage.

DISCU',ssION

The cast were extremely fine grained and showed no significant difference in size, a condition which prevailed after the metals had been rolled. The annealed specimens all exhibited grain growth. The oomparative grain sizes of the various alloys is shown in Table I.

Table I Relative Grain Sizes of .1.110s After Annealin :Treatment :Pure Zinc: 1 Te : Te: ..• b Cast • 0.145 mm:0.102 . mm: mm: • d Rolled • 0~l4l mm:0.147 mrn: mm: • t Thin sheet: 0.098 mm:0.097 mm: mm: From the above table it can be seen that there is no marked differenoe 1n grain size between zinc and the zinc tellurium alloys and that the addition of small -7- amounts of tellurium may tend to increase the grain size. The effect of _alloying small amounts of copper and magnesium with zinc (5) has been found to toughen it and greatly improve its mechanical properties. While the effect of small amounts of copper and magnesium on the structure of zinc has not been studied, it might, in part, exert a notable effect on the grain size of zinc and a metallographic study of these alloys might prove of value.

SUMMARY 1. The addition of small amounts of tellurium to zinc does not cause any marked effect on grain growth. 2. The addition of small amounts of tellurium to zinc improve its rolling qualities at ordinary temp- eratures.

(5) "Effect of Alloying on Zinc Roofing Design"t Trans. A I M E, Institute of Metals Division, pp 481 (1930J -8-

BIBLIOGRAPHY Hayward, Outlines of Metallurgical Practice Liddell and Doan, Principles of Metallurgy Peretti, Alloys of Lead and Tellurium Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chem18t~, Volume XI ACKNOWLEDGEMENT I wish to thank Dr. Curtis L. Wilson and Professor J. U. MaoEwan for their aid and advise during the investigation of this thesis.