Dynamic constitutive relationship of TiZrHfCu0.5 high entropy alloy based on Johnson-Cook model

Abstract

High entropy alloy has attracted much attention in the field of national defense due to their excellent low-temperature dynamic mechanical properties. Taking TiZrHfCu0.5 high entropy alloy as the research object, the compressive properties of the specimens under quasi-static and dynamic (strain rate range 600s−1-2600s−1 and temperature range −60 °C–20 °C) conditions are systematically tested. Based on the static/dynamic stress-strain experimental results, the parameters of the original Johnson-Cook constitutive model are determined by fitting. On this basis, a modified Johnson-Cook constitutive model considering the coupling effects of strain, strain rate and temperature is proposed and its parameters are determined. The dynamic compression process of the specimens under different strain rates and temperatures is numerically simulated by ABAQUS finite element software, and the accuracy of the modified Johnson-Cook constitutive model to predict the dynamic compression behavior of TiZrHfCu0.5 high entropy alloy is verified. The experimental and numerical simulation results show that the TiZrHfCu0.5 high entropy alloy exhibits significant strain rate hardening effect and excellent low-temperature mechanical properties during dynamic compression. The ultimate stress can reach 1.79 GPa at −20 °C and strain rate of 2600 s−1. The predicted curves of the modified Johnson-cook constitutive model are in good agreement with the experimental results at low temperature and high strain rate. The modified Johnson-Cook constitutive model is embedded in the finite element software, which effectively improves the reliability of the numerical simulation of the compression performance of TiZrHfCu0.5 high entropy alloy at high strain rate and low temperature. The relative error between the predicted results of the modified Johnson-Cook constitutive model and the experimental results is greatly reduced.