Study on Constitutive Characteristic of As-Cast AA6061 Alloy under Plane Strain Compression Based on Orthogonal Analysis

Constitutive relationship and microstructure evolution of as-cast AA6061 alloy were studied using plane strain compression (PSC) under the temperature of 300–450°C, the strain rate of 0.01–5 s−1, and the strain of 0.9. It is found that the flow stress decreases with increasing temperature and decreasing strain rate. The dynamic recovery (DRV) and recrystallization (DRX) are found to easily occur by optical microscopic (OM) techniques. The softening mechanisms are mainly due to DRV that is accompanied by a slight DRX. Based on orthogonal analysis, the strain should be taken into account to derive the constitutive model accurately, and the interaction effect between the strain rate and temperature on the stress can be neglected when compared with the individual effect of the strain rate and temperature. The strain-compensated constitutive models based on orthogonal experiment are established, and the activation energy Q is found to be 158.465 kJ/mol. The correlation coefficient and the average absolute relative error between the experimental and the predicted results are 0.9946 and 4.2656%, respectively. The developed models can be used to predict the stress precisely at a wide range of strains, strain rates, and temperatures.