Constitutive model development and hot extrusion simulation for AZ61 magnesium alloy

Abstract

Compression tests for the AZ61 magnesium alloy have been carried out at temperatures ranging from 200 to 400°C and with different strain rates from 10⁻³ to 5 s⁻¹. The flow stress–strain curves show that the flow stress reaches a peak value and then decreases to a steady value. This steady value decreases with rising temperature and decreasing strain rate. A new constitutive model is developed to describe flow stress as a function of temperature T, strain rate ϵ, strain ϵ, and strain softening coefficient which is introduced into the simulation (final element method) of hot bar extrusion. The simulation results show that stress is relatively high around the entrance of the conical die, while the highest temperature and the largest strain appear near the exit of conical die. By comparing the simulation and experiment result, successful extrusion temperature and speed are 300°C and 10 mm s⁻¹ respectively.