CONSTITUTIVE ANALYSIS OF Cu-DHP ALLOY DURING HOT COMPRESSION

The hot deformation behavior of deoxidized high-phosphorus copper (Cu-DHP) was investigated during compressive deformation over a wide deformation temperature range of 200 to 1000 °C and strain rates ranging from 0.0005 to 0.4 s^-1. The flow curves related to the hot working regime (500 to 1000 °C) generally showed distinct peak stresses followed by a drop in flow stress after the peak point, revealing the occurrence of dynamic recrystallization (DRX). By increasing the Zener-Hollomon parameter, the cyclic flow curves were replaced by the single-peak ones and eventually to the characteristic dynamic recovery (DRV) curves. At temperatures below half the melting point, only DRV-type curves were observed. Constitutive analysis yielded an apparent activation energy of 274.1 kJ/mol, a hyperbolic sine power of 4.88, and a power law stress exponent of 5.27, resulting in flow stress equations describing material flow in the hot working regime. Moreover, the power law breakdown and the importance of deformation temperature during thermomechanical processing were also critically discussed based on the mathematical fitting, strain rate sensitivity index, and microstructural analysis for investigating grain refinement by DRX. Furthermore, a strain-compensated Arrhenius model was developed for prediction of flow curves, considering the initial flow hardening and the subsequent flow softening by DRX. These findings offer practical guidance for optimizing hot working conditions of Cu-DHP alloy, with deformation at high Zener-Hollomon parameters enabling full DRX and finer grain structures for improved performance.