Dislocation kinetics explains energy partitioning during strain hardening: Model and experimental validation by infrared thermography and acoustic emission

Abstract

The energy dissipation and storage during strain hardening of metals have been investigated by means of complementary in situ techniques - infrared thermography (IRT), digital image correlation (DIC) and acoustic emission (AE). Inspired by experimental results obtained in the present work and data available in literature, we proposed the analytically tractable thermodynamic modelling approach, which is conceptually based on a single-variable dislocation evolution approach with a total dislocation density serving as a principal variable governing the strain hardening process. Unified by the kinetic approach involving generation, annihilation and motion of dislocations, the models accounting for the acoustic emission behaviour and heat dissipation under load have been proposed and verified experimentally. For the first time, we were able to demonstrate that the key parameters governing the dislocation storage and annihilation rates can be, in principle, recovered from independent AE and IRT measurements. These results agree favourably with the predictions of the dislocation-based constitutive strain hardening models of the Kocks-Mecking type. The self-consistency, versatility and predictive capacity of the proposed modelling approach are demonstrated in the examples of Cu–Zn alloys with different concentrations of Zn varied from 0 to 30% and correspondingly different stacking fault energies.