Abstract: The 10 mm thick wear resistant Al-Si-Cu alloy plates were double-side friction stir welded(D-FSW).The microstructure and mechanical properties of the joints were investigated.The results show that the as-cast Al grain and Si reinforcement particles in the weld are remarkably refined during friction stir welding.The distribution of Si particles in the weld is more uniform than that in as-received base metal.The refinement of the grains and the uniformity of Si particles in the second pass are better than those in the first one.The joints of double pass welding in opposite direction(OD joints) exhibit lower tensile strength than those of double pass welding in the same direction(SD joints).All the OD joints fractured through the advancing side of the joints,while the fracture paths of SD joints depend on the welding parameters.The tensile strength of SD joints welding at a stirring tool rotating speed of 950 rpm and a welding speed of 10 mm·min^-1 is up to 87.4% of the base metal.