Wrought Magnesium Alloy AZ31 Grain Refinement by Predeformation

摘要

Lightweight BIW (body in white) has become one of the challenges for automotive OEM companies. Magnesium alloys become one of the options because of its high specific strength. However, the fabrication cost of wrought Mg alloys is still pretty expensive due to its coarse grained structure. Wrought magnesium alloy AZ31 as cast with an initial grain size of over 500 μm was studied. Grain refinement is achieved by means of predeformation process at elevated temperature. It was found that predeformation process could significantly affect the mechanical properties of the final products. Predeformation made between at low temperatures and high temperatures appears to be quite different which determine the macro mechanical properties. An anisotropic structure is found after predeformation at as low as at strain of 0.05. Dynamic recrystallisation has been seen one of the effective methods to refine the grain structure of wrought magnesium alloy for better mechanical properties, which is shown strong dependence on the occurrence of twinning process. Metallographic analysis was used to explain the microstructural evolution during the deformation process.