Constitutive analysis of Cu-DHP alloy during hot compression

The hot deformation behavior of the deoxidized high-phosphorus copper (Cu-DHP) was investigated during compressive deformation at 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 with the fall of 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 finally by the characteristic dynamic recovery (DRV) curves. At temperatures lower than half of the melting point, only DRV-type curves were observed. Based on the constitutive analysis, the apparent activation energy of 274.1 kJ/mol, hyperbolic sine power of 4.88, and power law stress exponent of 5.27 were obtained, resulting in the flow stress equations to describe 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.