Abstract
Magnesium alloy generally has plastic anisotropy in mechanical properties due to hexagonal close-packed lattice structure and large differences among critical resolved shear stress of slip and twin systems. This study aimed to change the mechanical properties in a selected area of AZ31 Mg alloy thin-walled circular tube to meet the demands of products. First, the uniaxial tension-compression tests and compression-tension tests were conducted to investigate the influence of load reversal on the mechanical responses concerning the twin deformation. It was found that the strain hardening phenomenon in the deformation after the load reversal was strongly influenced by the pre-straining. Next, the localized bulging deformation was applied to the selected area to activate the extension twinning. The bulged area was then restored to its original profile by press forming in the radial direction of the circular tube. The activation of twinning in the bulged area was confirmed by the electron backscatter diffraction (EBSD) analysis. The change in the mechanical properties in the bulged area was investigated by the uniaxial tensile test and micro Vickers hardness test. The obtained results revealed that the bulged area exhibited better ductility as well as the higher flow stress than the initial state, with the aid of mechanical twinning.
