Optimizing the mechanical properties of Al-Si alloys through friction stir processing and rolling

In this study, hypoeutectic and eutectic Al-Si alloys were processed through rolling and friction stir processing (FSP), and the effects of deformation routes on the microstructures and mechanical properties of Al-Si alloys were studied. FSP led to the fragmentation and uniform distribution of Si phases in the Al matrix and then eliminated the preferential crack propagation channels of Al-Si alloys during tensile tests. The optimized crack propagation path and high work hardening rate led to a tensile elongation of as high as 39% in FSP Al-7Si alloys. Further rolling refined the Al grains and introduced dislocations into the Al-Si alloys. The fine Si phases, tens of nanometers is size, in the FSP samples promoted grain refinement after rolling. Compared with the Al-Si alloys subjected to warm rolling only, the alloys subjected to FSP and warm rolling exhibited higher strength and ductility. FSP alloys with the highest strength were achieved through cold rolling because of high grain boundaries and dislocation-strengthening effects. This work provided a method for fabricating Al-Si alloys with excellent mechanical properties by combining FSP and rolling.