Examination of high-temperature mechanisms and behavior under compression and processing maps of pure copper

초록

The hot compression behavior of pure copper (commercial grade) was studied in a temperature range between 843 and 993 K and in a strain rate range between 10(-3) and 10 s(-1). The activation energy for plastic flow was determined to be 215 kJ/mol, which is similar to the activation energy for lattice diffusion in copper ( = 197 kJ/mol). The stress exponent values associated with the plastic flow were 7-9, which are larger than the theoretical values associated with lattice-diffusion controlled dislocation climb creep (4.5-5). A comparison of the current data with the data obtained from the creep tests performed on the pure copper at low strain rates by other investigators in a similar temperature range revealed that the most of the data studied in this study belong to the regime where power-law breakdown occurs. Processing map constructed at a strain where steady-state plastic flow was observed showed that the power dissipation efficiency was low (<= 21%) in the entire experimental ranges of strain rate and temperature. Discontinuous dynamic recrystallization (DDRX) associated with a single peak or multiple peaks in the stress-strain curves occurred during the first stage of plastic deformation. Dynamic recovery occurred after the DDRX activity ended, leading to the formation of a subgrains with low-and intermediate angle grain boundaries within the recrystallized grains with high-angle grain boundaries. Due to the formation of extensive substructure within DDRX grains, the fractions of high-angle grain boundaries measured after the compressive deformation were low (<= 30%). (C) 2019 The Authors. Published by Elsevier B.V.

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