SiC_p/2A14复合材料厚板FSW接头微观组织与力学性能

FSW butt welding was attained for the 20 mm thick plates of SiC_p/2A14 reinforced aluminum matrix composite with 15% in SiC volume fraction, and the microstructure and mechanical properties of the joint were analyzed. The results show that the composite welded joint can be divided into four zones, which are the base material (BM), heat-affected zone (HAZ), thermo-mechanical affected zone (TMAZ) and nugget zone (NZ). Among them, the base material microstructure presents a rolled strip organization, which is coarsened by heat in the HAZ. In the TMAZ, the extruded streamline microstructures composed of fine grains can be observed, and the strip microstructure in the NZ disappears, and a uniformly fine equiaxed grains are formed. Moreover, the SiC particles and white phase Al₄C₃ in the NZ are fully refined and distributed in a diffuse and uniform manner. The lowest value of microhardness of the joint is observed at the interface of the HAZ and TMAZ, which is also the place where fracture occurs. The tensile strength, yield strength and elongation of the joints are 278 MPa, 255 MPa and 2.77%, respectively, which reach 83.91%, 77.62% and 71.76% of the BM, respectively. A maximum local strain of 16.8% at fracture is observed with digital image correlation method (DIC). The joint fracture mode is a mixed fracture mode of ductile fracture and brittle fracture.