MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Effects of Natural Aging on Age-Hardening Behavior of Cu-Be-Co and Cu-Ti Alloys Severely Deformed by High-Pressure Torsion
M. HibinoC. WatanabeY. TsujiR. MonzenY. TodakaW. Sato
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2017 Volume 58 Issue 10 Pages 1346-1350

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Abstract

Solution-treated Cu-1.8 mass%Be-0.2 mass%Co and Cu-3 mass%Ti alloys were subjected to severe plastic deformation using high-pressure torsion (HPT) process to examine the change in densities of grain boundary, dislocation and vacancy during natural aging of the two alloys at 293 K after HPT-straining, and the influence of the natural aging on the age-hardening behavior of the alloys on subsequent artificial aging. Application of HPT processing under an applied pressure of 5 GPa for 10 revolutions at 1 rpm to each alloy produced an ultrafine-grained structure. Aging the HPT-processed alloys at 293 K for the longest period of 2.59 Ms (1 month) did not essentially change the dislocation densities and grain sizes of the alloys; however, the vacancy concentrations of the alloys gradually decreased with increasing natural aging time. The attained peak hardness of the Cu-Be-Co alloy on subsequent artificial aging at 593 K decreased as natural aging time increased, while the natural aging at 293 K for 2.59 Ms had no influence on the age-hardening behavior of the Cu-Ti alloy during artificial aging at 623 K. This result is ascribed to the difference in formation mechanisms of strengthening precipitates between two alloys; G.P. zones are directly formed in Cu-Be-Co alloy while β'-Cu4Ti phase is formed via spinodal decomposition without nucleation events in Cu-Ti alloy.

 

This Paper was Originally Published in Japanese in J. Japan Inst. Copper 55 (2016) 197–201.

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© 2017 Journal of Japan Institute of Copper
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