Effect of grain size and strain rate on tensile work hardening behavior of two different FCC metals

Abstract

The present work aims to investigate the effect of grain size and strain rate on tensile work hardening behaviour of two single-phase FCC metals having different stacking fault energy (SFE); commercially pure polycrystalline Cu and pure Al. Different heat treatment processes were employed to produce different grain sizes in the materials. The samples with different grain sizes were then subjected to uniaxial tension test with strain rates in the ranges 10−4 to 10−1 s−1. The work hardening behaviour was analysed using two different approaches: Hollomon analysis and Kocks-Mecking analysis. The Kocks-Mecking analysis proves to be a better assessment technique of the work hardening behaviour of the two investigated materials as compared to the Hollomon analysis. A clear difference in work hardening behaviour between Cu and Al is noted from Kocks-Mecking analysis. Further, the Hollomon analysis doesn’t show any effect of grain size and strain rate on the work hardening behaviour. Whereas, Kocks-Mecking analysis revealed that both grain size and strain rate affect the 2nd and 3rd stage of work hardening behaviour in the case of quenched Cu. An important component of hardening in Kocks-Mecking analysis: the athermal component of strain hardening rate (θh) is found to be approximately equal to the average work hardening rate at the initial stage (stage I) of plastic deformation for both Cu and Al.