Alleviation of Mechanical Anisotropy in Ultrafine/Nano-grained AZ31 Magnesium Alloy

An ultrafine/nano-grained AZ31 magnesium alloy was processed through multipass accumulative back extrusion at 280 and 380 °C. Texture analysis was conducted to determine preferred crystallographic orientations developed during multipass deformation. The anisotropy in mechanical properties of the processed materials was studied by compressive and tensile testing. The results implied that the accumulative back extrusion effectively reduces the anisotropy of yield strength, ultimate strength and strain-to-fracture during compressive and tensile loading. The operations of different twinning/slip systems during compressive and tensile deformation were discussed using Schmid factors measurements. A decrease in twinning-related anisotropy, as well as the contribution of different slip systems in strain accommodation, could reduce the mechanical anisotropy of ultrafine/nano-grained AZ31 alloy. The compressive strength of the two-pass processed material was lower along extrusion direction than transverse direction; however, the result was reverse after four passes. The tensile behavior implied that the contribution of basal slip might accommodate strain along length as well as the thickness of the specimen, while prismatic slip may assist in narrowing the width of the specimen and elongating the length.