Reassessment of temperature increase and equivalent strain calculation during high-pressure torsion

Abstract

The problems of temperature increase during high-pressure straining and equivalent strain calculation are reassessed on the basis of general considerations and experimental evidence. Temperature evolution is measured for some pure fcc and hcp metals (Cu, Al, Ni, Ti and Zr) and different regimes of HPT (pressure, strain accumulated and strain rate). The results obtained are compared with modelling and theoretical estimates. A simple model taking into account microstructure evolution during HPT is applied in order to explain the consequent "straining-hardening-softening". The heat release of plastic work is calculated on the basis of both the von Mises and Hencky equivalent strains giving some assessment on the applicability of these equations.