Material sensitivity and formability prediction of warm-forming magnesium alloy sheets with experimental verification

Abstract

This paper proposes a theoretical method for predicting the formability of magnesium alloy sheets at elevated temperatures by combining the Marciniak and Kuckzinsky model with the Logan–Hosford yield criterion. In addition, the material sensitivity under different strain rates from 0.001 to 0.1 s−1 and elevated temperatures on forming the magnesium alloy was also investigated in this study. Forming limit tests on AZ31B magnesium alloy sheets were performed concurrently for the theoretical forming limit diagram (FLD) verification using a self-developed forming facility at elevated temperatures of 200, 250, and 300 °C and, simultaneously, the material sensitivity effect under a selective strain rate of 0.01 s−1. Based on the verified FLD prediction results, numerical simulations of warm-forming a AZ31B camera casing of thickness 0.8 mm as an example were then carried out. The warm forming experiments for this camera casing, under the identical conditions, were also performed for verification. As a consequence, it was found that the effect of strain rate on the prediction of FLDs did have a significant influence with increasing temperatures. Furthermore, the results of numerical simulations showed a good agreement with those of the warm forming experiments at different elevated temperatures. The proposed theoretical method offers a relatively accurate prediction in warm-forming magnesium alloy sheets and should lead to a remarkable reduction of trials, at least in the sense of both time and cost benefits, before a large batch production. Such outcomes of the study are expected to be very helpful and contributive to professionals, engineers, and the magnesium alloy-related applications in industry.