High temperature composite forming limit diagrams of four magnesium AZ31B sheets obtained by pneumatic stretching

► We investigate the hot formability of four Mg AZ31 sheets by pneumatic stretching. ► Forming limits are highly dependent on biaxial strain ratio and sheet orientation. ► Orientation effects on material FLCs are best represented by a “composite FLD”. ► Differences in processing routes significantly affect material formability limits. ► Oxide stringers promote coalescence of cavities, which leads to premature failure.