Microstructure and mechanical properties of friction stir welded AC4A + 30 vol.%SiCp composite

• The AC4A + 30 vol.%SiC PRAMCs were welded by FSW for the first time.
• Tensile properties of the welds were higher than the joints.
• The conglomeration of SiC particles was observed in the upper weld.

AC4A + 30 vol.%SiC particulates reinforced aluminum matrix composite was friction stir welded successfully. The influences of welding parameters on microstructure and mechanical properties of joints and welds were investigated. The results show that defect-free joints could be obtained in the welding speed range of 25–150 mm/min at a constant rotation speed of 2000 rpm. The optimum ultimate strength (UTS) of the joint is up to 140 MPa, while the optimum UTS of the weld is 279 MPa which is 1.72 times that of base material. The microstructure analyses indicate the reason for higher weld strength. On one hand, SiC particles are fractured and thus fined due to the intensive stirring action of tool pin during Friction Stir Welding (FSW). On the other hand, the plastic flowing of material in the weld is benefit to eliminate microporosities existed in original base material. In addition, higher welding speed causes the conglomeration of SiC particles in the upper section of the weld, which leads to inconsistent deformation between the upper section and the lower section in the weld zone (WZ) during tensile test, and thus resulting in the decrease of weld strength.