Effect of multi-pass friction stir processing on microstructure and mechanical properties of SiC_P/2A14 aluminum alloy composites

The SiC particle reinforced 2A14 aluminum alloy (SiC_P/2A14) composite was treated by friction stir processing (FSP) technology. The metallurgical characterization, electron backscatter diffraction (EBSD), SEM, hardness test and mechanical tensile test were used to analyze the influence of the multi-pass FSP on the microstructure, mechanical properties and superplastic deformation behavior of the SiC_P/2A14 composite. The results show that the distribution of SiC particles in the SiC_P/2A14 composite stirring zone is obviously uniform and the grain is refined after FSP. The grain size of the SiC_P/2A14 composite with 2-pass of FSP is the smallest, which is 3.14 μm. With the increase of processing passes, the hardness of the SiC_P/2A14 composite decreases, and the tensile strength at room temperature and the elongation at high temperature both increase first and then decrease. Among them, the SiC_P/2A14 composite with 2-pass FSP reaches the peak, and the tensile strength at room temperature is 319 MPa, which is 41% higher than the SiC_P/2A14 composite without FSP, and the elongation is 609% at 500℃ and the strain rate is 1×10⁻³ s⁻¹, which is 133% higher than the SiC_P/2A14 composite without FSP.