Surface Modification of Magnesium Alloy Performed by Friction Stir Processing

Surface modification of AZ31 magnesium alloy was conducted by friction stir processing(FSP) and Al_2O_3 particles addition.The microstructure of surface composites,mechanical properties and the effect law of processing speed on the microstructure were studied.The results show that Al_2O_3/AZ31 surface composite layer could be successfully fabricated by the processing.Al_2O_3 particles were uniformly distributed in magnesium matrix and the surface composites had excellent bonding with the magnesium alloy substrate when the rotating rate was 1 500 r·min~(-1) and processing speed was 23.5 mm·min~(-1).The grains were refined because of the excellent pinning effect of Al_2O_3 particles.The microhardness of composite surface was 55 HV,which was increased by 41% compared with that of the AZ31 substrate.Both the grain refinement and the reinforcement increased the microhardness.