Forging characteristics of AZ31 Mg alloy

Characteristics of open die forging in an AZ31 Mg alloy and a relation betw een microstructure and mechanical properties of the forged alloy have been investigated fur an as-received specimen and an extruded specimen, where th e as-received specimen consisted of both elongated coarse grains and equiax ed small grains, and the extruded specimen consisted of only equiaxed small grains. Each specimen was forged at 323 to 673 K. In addition, tensile tes ts of the forged specimens were carried out at room temperature and the mic rostructure was observed using an optical microscope. In the forging tests, the specimens could be forged from 18 mm to 2.5 mm in thickness at forging temperatures of more than 423 K. In particular, the specimen could be forg ed without surface c-racks when the grains were refined by extrusion prior to forging. However, for the as-received specimen, some cracks were observe d at the edge of the specimens forged at less than 573 K. Therefore, it is suggested that the microstructure of the pre-forged specimens needs to he h omogeneous, in order to attain a good surface quality, when forging is carr ied out at temperatures less than 573 K. The grain size of the forged speci mens decreased with decreasing forging temperature. IL should be noted that a very small grain size of about 3 mum was attained by forging at 473 K. T he tensile strength and the 0.2% proof stress of the forged specimens incre ased with decreasing forging temperature due to grain refinement by forging .