PLEASE 00 NOT REMOVE FRCM LIBRARY IRIL _ _ 1i'--8810__ ---' Bureau of Mines Report of Investigations/1983 Magnetic Properties of Synthetic Mischmetal Alloyed With Cobalt, Copper, Iron, and Magnesium By J. W. Walkiewicz. M. M. Wong. and E. Morrice UNITED STATES DEPARTMENT OF THE INTERIOR Report of Investigations 8810 Magnetic Properties of Synthetic Mischmetal Alloyed With Cobalt, Copper, Iron, and Magnesium By J. W. Walkiewicz, M. M. Wong, and E. Morrice UNITED STATES DEPARTMENT OF THE INTERIOR James G. Watt, Secretary BUREAU OF MINES Robert C. Horton, Director Library of Congress Cataloging in Publication Data: \\ a I k i e wi c z, J. W. (J 0 h n \\,) Magneric properties of synlhetic rnisl:hrncl,ll "lloy"d with "0),,11(, C{)PP<':f) iron, nlhJ magnesium. (Hcport of inves[ig~[inns / lJnilcJ Siales Departrnenl "f lh~ Illlcri­ or, Hure"u of Mines: 8810) Bibliography: p. 13. Supt. of Due." no,: I 28.23:8810, 1. Misehnlc[al-MOlglll:tic prorerti,'s, 2. Magneli,' "llo"s. l. Wong, M. M. (Morton Min), 1924- II, Morrice, I':. (hl\\'"r"). III. rirl<:. IV •.:-;crirs: Hcporr of invesrigarions(l'nire,j :-;lOlICS. !lurc"" of Mines): H810. TN23.U43 [TNfl93.R31 fl22s I fl20. ! 'H9291 83fj0022R CONTENTS Abstract ••••.•••••••..•..••••••••.•••••...••.••...•••••••....•••••..••••••••.•• Introduction................................................................... 2 Experimental procedures and equipment............................... ••..••..... 3 Alloy preparation......................................................... 3 Powder preparation........................................................ 3 Alinement and compaction.................................................. 4 Sintering................................................................. 4 Magnetic property measurements..................................................................................... 4 Results and discussion......................................................... 4 Magnetic propel,ties of M50-Co-Cu-i'lg....................................... 5 Effect of mischmetal content. ••• ••••..• ••••.....•••••....•...•. .••..• 5 Ef fect of copper content............................................. 5 Ef fect of magnesium content.......................................... 5 Ef fect of grinding................................................... 6 Magnetic properties of M30-Co-Cu-Mg....................................... 6 Ef fect of mischmetal content......................................... 6 Effect of copper content............................................. 7 Magnetic properties of M20-Co-Cu-Mg....................................... 7 Effect of mischmetal content......................................... 7 Effect of copper content............................................. 7 Effect of magnesium content.......................................... 8 Ef fect of grinding................................................... 8 Magnetic properties of M10-Co-Cu-Mg....................................... 9 Effect of mischmetal content......................................... 9 Effect of copper content............................................. 9 Magnetic properties of M-Co-Cu-Mg: Effect of lanthanum content........... 10 Magnetic properties of M-Co-Cu-Fe-Mg: Effect of iron content............. 11 Summary •••.••••••••••.•.••••••••••••••••.••••••••••.•.••....•••.••••.•••••.••. 12 References. .••..••••••.•••••.•••.•••••••.••••••••••••••••••••..••••••••. •. ••••. 13 Appendix.--Definitions of basic magnetic properties of a permanent magnet...... 14 ILLUSTRATIONS I, Effect of mischmetal content on the magnetic properties of M50-Co-Cu-Mg alloys. • • • • • • .• . • • • . • . • • . • . • . • • • . • • • • • • • • • • • • • . • • • •• • • • • • . • . • • • • . • 5 2. Effect of copper content on the magnetic properties of M50-Co-Cu-Mg alloys 5 3. Effect of magnesium content on the magnetic properties of M50-Co-Cu-Mg alloys. • . • • • • • . • • • • • • • • • • • • • • • . • . • • • • • • • • . • • • • • • . • • • • • •• . • . • • • • • • . • • 6 4. Dependence of magnetic properties on the comminution time of M50-Co-Cu-Mg alloys. • • • • • • • • . • • • • . • •• • • • • . • . • • • • . • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • 6 5< Effect of mischmetal content on the magnetic properties of M30-Co-Cu-Mg alloys. • . • • . • •• . •• • . • • . • • • • • • . • • . • • • . .. .• . • . • . 7 6. Effect of copper content on the magnetic properties of M30-Co-Cu-Mg alloys 7 7. Effect of mischmetal content on the magnetic properties of M20-Co-Cu-Mg alloys. • • • • • • • • . • •• • • • • • • • • • • . • • • • • • • • . • . • • • • . • . • • • • • • •• . • • • • • • • • • • • • • • 8 8. Effect of copper content on the magnetic properties of M20-Co-Cu-Mg alloys 8 9. Effect of magnesium content on the magnetic properties of M20-Co-Cu-Mg alloys. • • . • • • . • • . • • • • • • • • . •• • • • • • • . • • • • • • • • . • • • • • . • • • • • • • • • • • • •• • • • 8 10. Dependence of magnetic properties on the comminution time of M20-Co-Cu-Mg alloys ......... « •••••••••••••••••••••••••••••• "o •••••• " ••••••••••••••••• 9 11. Effect of mischmetal content on the magnetic properties of M10-Co-Cu-Mg alloys ......... t ......................................................... 9 ii ILLUSTRATIONS--Continued 12. Effect of copper content on the magnetic properties of MIO-Co-Cu-Mg all()ys................................................................... 10 13. Effect of lanthanum llnd copper on the mago<:tlc properties of a 36.5-pct-M allc)y ........ " ................ 10 ..... ,. 41 II> • ,. ,. " • 'II •• If .... , • ,. ...... " • .. • .. • .. • .. • .. • • • .. .. • • • • • 11 14. Effect of lanthanum and copper on the magnetic properties of a 37-pct-M a 110 Y .. ,. ....................... If .... r .. III .......... " ..... " ..................................... 111 " ........... /I 11 ]5. Effect of iron on the magnetic properties of MSO-Co-Cu-Fe-Mg alloys...... 12 16. Effect of iron on the magnetic properties of M20-Co-Cu-Fe-Mg alloys...... J2 A-I. HysterEsis loop of a permanent magnet materiaL.......................... 14 TABLES 1. Composition of M-Co-Cu-Fe-Mg alloys prepared arc melting.............. 3 2. Effect of composition 00 the magnetic properties of H-Co-Cu-Hg alloys.... 10 USED IN THIS REPORT °C degree Celsius MGDe mega-gauss-oersted em ce n t 1me ter MFa megapascal g gram min mi nute h hour \.lm micrometer kG kilogauss pct percent kOe kilooersted psi pounds of force per square inch MAGN ETIC PROPERT IES OF SYNTHETIC MISCHMET Al AllOYED WITH COBALT, COPPER, IRON, AND MAGNESIUM By J. W. Walkiewicz, I M. M. Wong, 2 and E. Morrice I ABSTRACT The Bureau of Mines investigated alloys containing lanthanum (La), praseodymium (Pr), neodymium (Nd), cobalt (Co), copper (Cu), iron (Fe), and magnesium (~g) as possible components of a permanent magnet mate­ rial utilizing a cerium-free synthetic mischmetal (M) as a substitute for scarce samarium (Sm) metal. Magnets containing M-Co-Cu-Mg and M-Co-Cu-Fe-Mg were fabricated by powder metallurgy techniques and evaluated. A synthetic mischmetal (M20) containing 20 pct La, 60 Pr, and 20 Nd yielded the best overall magnetic properties. The M20-Co-Cu-Mg alloys had energy products as high as 13.2 MGOe, rernanences as high as 7.89 kG, normal coercivities as high as 6.26 kOe, and intrinsic coercivities as high as 13.4 kOe. The best value of intrinsic coercivity, 22.9 kOe, was obtained with an M-Co-Cu-Mg magnet in which the synthetic misch­ metal contained 30 pct La, 50 Pr, and 20 Nd. These values compare fa­ vorably with those of the Sm-Co magnets fabricated and measured at the Bureau's Reno Research Center, which had energy product of 15.1 MGOe, remanence of 7.8 kG, normal coercivity of 7.5 kOe, and intrinsic coercivity of 27.4 kOe. Iron substitution for part of the cobalt re­ sulted in a decrease of magnetic properties, although several percent iron can be added before a drastic loss of magnetic properties occurs. 1Metallurgist, Reno Research Center, Bureau of Mines, Reno, Nev. 2supervisory chemical engineer, Reno Research Center, Bureau of Mines, Reno, Nev. (now retired). 2 INTRODUCTION Samarium is a scarce metal which is im­ Even though the addition of copper and portant for Sm-Co magnets in national magnesium to MM-Co increased the coerciv­ defense applications and in energy­ ity, a substantial loss of remanence and efficient electrical devices. The "pre­ energy product occurred. This prompted ferred status" of Sm-Co has created a the Bureau of Mines to conduct an inves­ demand for samarium metal that exceeds tigation to develop a synthetic misch­ production. The need to alleviate the metal (M) with values of remanence and demand for samarium has stimulated re energy product comparable to those of search on (MM,Sm)-Co Cl_, 1,~, lQ-Q) 2 Sm-Co alloys: energy product 15.1 MGOe, and MM-Co (4-5, 8-11) magnets in which remanence 7.8 kG, normal coercivity 7.5 natural mischmetal (MM) replaces part or kOe, intrinsic coercivity 27.4 kOe. The all of the samarium. initial rare-earth mixture of 50 pct La, 30 Pr, and 20 Nd was selected for the The term "natural mischmetal" denotes following reasons: a mixture of the light rare-earth met­ als consisting of 23-27 pct La, 4-7 Pr, 1. Cerium was eliminated because Ce-Co 10-,14 Nd, and 50-55 Ce. This is approxi­ had the lowest theoretical value of mag­ mately the same ratio of rare-earth netization (l, 2), which was confirmed by elements found in natural ore. A previous Bureau research. samarium-free, high-intrinsic-coercivity