Microstructural investigation of twin-roll cast magnesium AZ31B subjected to a single monotonic compressive stress

Abstract In this research paper the microstructure of the magnesium AZ31B alloy is investigated after the application of a single monotonic compressive strain of −0.4%. A band of twinned grains is observed to form in the test bar approximately 10 mm wide, corresponding to the zone of highest plastic strain. The microstructure of this region is studied using electron backscatter diffraction and transmission electron microscopy (TEM). Twinning mode and fraction are reported along with a detailed analysis of precipitate phase and size distribution. Evidence is given for twin-precipitate interaction during the twin formation process. High resolution TEM and energy dispersive X-ray spectroscopy are used in conjunction with structural simulation software to identify the Al-Mn phase. A zinc shell is observed forming around precipitates, and this is related to zinc exclusion by the precipitating Al-Mn phase.