Morphology of oxide and interface structure in AZ31B magnesium alloy prepared by solid state recycling

Abstract

Ultrathin AZ31B magnesium alloy chips were recycled by solid state recycling process at different extrusion ratios. The morphology and distribution of the oxide in recycled magnesium alloy were characterised, and the interface structure between the oxide and magnesium alloy matrix was investigated by means of high resolution transmission electron microscopy. The results indicate that the oxide film introduced from the surface of the chip was broken up in the process of extrusion. MgO shows a nanoscale spherical particle and homogeneously distributes in some tiny areas in the magnesium alloy matrix. In the investigated extrusion ratio range, the diameter of the MgO particle differs little. However, the oxide film was not broken up completely in the recycled alloy with low extrusion ratio. The oxide particle exhibits good bonding with the magnesium matrix. The dispersion strengthening of MgO particle will contribute to the higher strength of recycled magnesium alloy, whereas the good bonding of MgO and magnesium matrix is the prerequisite.