Processing maps and rate controlling mechanisms of hot deformation of electrolytic tough pitch copper in the temperature range 300-950 °C

The hot deformation behavior of electrolytic touch pitch (ETP) copper has been studied in the temperature range 300-950 °C and strain rate range 0.001-100 s−1 using isothermal hot compression tests. Processing maps are developed at different plastic strains with a view to characterize the dynamics of hot deformation while the standard kinetic analysis has been applied to evaluate the rate controlling mechanisms. The processing maps have exhibited three deterministic domains representing dynamic recrystallization (DRX) of ETP copper and occurring in the following temperature and strain rate ranges: (1) 400-600 °C and 0.001-0.01 s−1, (2) 650-950 °C and 0.001-3 s−1 and (3) 700-950 °C and 10-100 s−1. While all these domains merge with increasing plastic strain, the first domain has a lower efficiency of power dissipation, the second domain appears early in deformation (strain of 0.1) and the third domain occurs at larger strains (>0.2). The results on processing maps have correlated well with those obtained from kinetic analysis and the apparent activation energy values estimated in these DRX domains are 159, 198 and 91 kJ/mol, respectively, which suggest that dislocation core diffusion, lattice self-diffusion and grain boundary self-diffusion are the rate controlling mechanisms. In all the three DRX domains, the average grain diameter varies linearly with the Zener-Hollomon parameter.