The microstructure and mechanical properties of materials saturate to steady states after severe plastic deformation (SPD). Despite the well-known effect of temperature on the steady-state microstructure, there is no general agreement on the significance of strain rate and the applicability of the Zener-Hollomon parameter in this regard. In this study, several pure metals (aluminum, copper, titanium, and iron) and a Cu-30Zn (wt%) brass alloy have been processed by a high-speed high-pressure torsion (HPT) equipment with controllable rotation speeds in the range of 0.06 to 60 rpm. It is found that crystallite/grain size, dislocation density, microhardness and shear stress at the steady state are reasonably rate-independent for the von Mises strain rates in the range of 0.004 to 20 s-1. Because both rates of grain refinement and of dynamic recrystallization are proportional to the strain rate, it is suggested that their balance, which determines the steady state, is rate-independent.
@article{arxiv.2301.02805,
title = {Significance of Strain Rate in Severe Plastic Deformation on Steady-State Microstructure and Strength},
author = {Kaveh Edalati and Qing Wang and Nariman A. Enikeev and Laura-Jean Peters and Michael J. Zehetbauer and Erhard Schafler},
journal= {arXiv preprint arXiv:2301.02805},
year = {2023}
}