Evolution of tension and compression asymmetry of extruded Mg-Al-Sn-Zn alloy with respect to forming temperatures

Substantial strength of as-extruded and as-forged ATZ842 alloys is attributed to precipitation strengthening due to the presence of fine Mg2Sn and Mg(17)AL(12) particles in the alloys. Because Mg alloys inevitably undergo dynamic recrystallization during the warm forging that is required for their net-shape processing, it is important to examine microstructural evolution in as-forged samples. The appropriate forging temperature was found to range from 250 to 300 degrees C; average grain size started to increase at temperatures over 350 degrees C due to abnormal grain growth and a reduction in the fraction of second-phase particles. The ATZ842 alloy showed mechanical properties superior to those of the AZ80 alloy, including yield and ultimate strengths in both tensile and compressive deformations. Remarkably, the tension and compression asymmetry in plastic flow of ATZ842 forged at 250 degrees C was characterized by a yield ratio of about 1.02, compared to the yield ratio of 0.88 for the AZ80 alloy. (C) 2016 Elsevier Ltd. All rights reserved.