Effect of excess Au on antiphase domain growth in Cu 3 Au
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microscopy, followed closely the procedures used in the earlier work on the stoichiometric alloy. ~'z Briefly, the alloys as illustrated in the partial phase diagram in Fig. i were disordered by quenching from 450~ into water and then aged at various temperatures within the Cu3Au I ordered phase region. The APD structures produced by various aging treatments were studied with a Hitachi HU-IIA electron microscope operating at I00 kV. Average APD sizes were determined from 110 dark field images obtained from grains having (Ii0} foil norreals. As in the previous work, 2 the APD sizes were measured by lineal analysis with a circular test line /~25 I
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EXPERIMENTAL
PROCEDURE
T h r e e n o n s t o i c h i o m e t r i c Cu3Au a l l o y s w e r e o b rained from E n g e l h a r d I n d u s t r i e s in the f o r m of a s r o l l e d s t r i p ~0.25 cm • 2.5 c m . C h e m i c a l a n a l y s e s r e c e i v e d with the a l l o y s showed them to contain 25.98, 27.94, and 31.46 at. pct Au. S p e c i m e n p r e p a r a t i o n and heat t r e a t m e n t , as well as the p r e p a r a t i o n of thin foils for e x a m i n a t i o n by t r a n s m i s s i o n e l e c t r o n
300
275
250 15 C. L, RASE is with Central Foundry Division, General Motors Cor-
poration, Saginaw,MI 48603. D. E, MIKKOLAis Professor of Metallurgical Engineering,MichiganTechnological University, Houghton, MI 49331. Manuscript submitted May 24, 1974. METALLURGICALTRANSACTIONSA
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ATOMIC PERCENTAu Fig. 1--Schematic of a portion of the phase diagram of Cu-Au system showing alloy compositions studied in the current investigation. VOLUME 6A, DECEMBER 1975-2267
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Table I. Average Antiphase Domain Sizes for Initially Quenched CuaAu (Ref. 2) and CuaAu + Au Alloys given Various Annealing Treatments
375~
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Number o f Intercepts
0.5 3 10 20 45 50 100 20O
218 208 171 195 117 92 58
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Number of Intercepts
133 310 624 892 1333 1800 270O
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Cu-25.98 At. Pct Au 375~
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157 640 537 681 353 496 464
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HOURS Fig. 2--Average antiphase domain size vs time for initially disordered Cu-25.98 pct Au annealed at 375 and 320~ Error bars indicate the range of sizes from different micrographs, while the point is the average of the sizes. f,
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Cu-27.94 At. Pct Au 320 ~
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3 10 20 50 100 200 400 613 813 1000
434 385 679 490 887 599 433 257 314 276
346 623 894 1421 2099 2959 3707 4475 4361 4551
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