Influence of aluminum content on the texture and sheet formability of AM series magnesium alloys

Abstract

The fabrication of magnesium (Mg) alloy sheets with both high mechanical strength and superior cold formability was sought by optimizing the aluminum (Al) content of the alloy sheets. We investigated the influence of varying Al content from 3wt% to 8wt% on the texture, mechanical properties, and stretch formability of AM series Mg alloys, processed by high-temperature rolling. The ultimate tensile strength improved steadily from 247MPa to 303MPa with an increase in Al, due to solid solution strengthening. The basal texture intensity decreased with increasing Al content, reached a minimum value at 6wt% Al, and then increased as more Al was added. The weakest basal texture led to the smallest Lankford value and the largest strain hardening exponent in the AM60 (6wt% Al) alloy. The alloys with lower Al contents of 3–5wt% exhibited a high fracture elongation of 27%, which continuously decreased to 23% as the Al content increased to 8wt%. The AM50 alloy exhibited excellent stretch formability with the largest Erichsen value of 9.1, while the AM30 and AM80 alloys showed much smaller Erichsen values of 5.6 and 6.0, respectively. This can be attributed to a good balance among the decreased r-value, increased n-value, and enhanced tensile ductility in the AM50 alloy, despite its basal texture being slightly stronger than that of the AM60 alloy.