Surface Modification of Magnesium Alloy Performed by Friction Stir Processing

Surface modification of AZ31 magnesium alloy was conducted by friction stir processing(FSP)and Al2O3 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 Al2O3/AZ31 surface composite layer could be successfully fabricated by the processing.Al2O3 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 Al2O3 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.