Microstructural refinement and mechanical properties of direct extruded ZM21 magnesium alloys

Cast ZM21 magnesium alloys were subjected to symmetric extrusion at four different temperatures (200, 250, 300 and 350 °C) with three extrusion ratios of 4:1, 9:1 and 16:1, respectively. The effects of extrusion parameters such as temperature and extrusion ratio were studied by optical microscopy, X-ray diffraction (XRD) and tensile test. The optical micrographs exhibited various stages of recrystallization, i.e., partial to full recrystallization influencing mechanical properties to good extent. Higher extrusion temperature resulted in coarse grains, whereas finer grains were obtained at higher extrusion ratios. Ultimate tensile strength of this alloy was increased from 160 MPa to 316 MPa after extrusion at 250 °C with an extrusion ratio of 9:1.