Phenomenological Models to Predict the Flow Stress up to the Peak of as-Extruded 7050 Aluminum Alloy

Abstract

In order to improve the understanding of the hot flow behaviors of as-extruded 7050 aluminum alloy, a series of isothermal compression tests with a fixed height reduction of 60 % were performed at the temperatures of 573 K, 623 K, 673 K and 723 K, and the strain rates of 0.01 s−1, 0.1 s−1, 1 s−1 and 10 s−1 on a Gleeble-1500 thermo-mechanical simulator. Based on both nonlinear and linear estimations of work hardening rate versus strain curves, two phenomenological models have been developed to predict the flow stress values under different hot forming conditions up to the peak stress. The suitability levels of these two models were evaluated by comparing both the correlation coefficient (R) and the average absolute relative error (AARE). R-value and AARE-value for the linear phenomenological model are 0.9995 and 2.18 %, respectively, while the R-value and AARE-value for the nonlinear model are 0.9901 and 10.60 %, respectively. The results showed that the predictions of these two models were in good agreement with the experimental data for 7050 aluminum alloy. Fewer materials constants were involved in the linear model, and the predicting ability of the linear model is stronger than the nonlinear model.

Keywords

• hot flow behaviors
• 7050 aluminum alloy
• work hardening rate
• phenomenological models