Study On The Microstructure And Properties Of ZrB₂+AlN/Al Composite Materials Prepared Based On FSP

Aluminum matrix surface composites combine the excellent performances of aluminium matrix and surface reinforcement,which enlarges the application scope of aluminium alloy materials and attracts wide attention in engineering applications and scientific research fields.Friction Stir Processing(FSP),as a new processing technology,is suitable for surface modification of materials.It can effectively inhibit the interfacial reaction between particles and matrix and avoid the formation of intermetallic compounds.In this paper,a special stirring head friction stirring process was used to fabricate the composite layer on the surface of aluminum matrix with different proportion of reinforcement phase.After setting the parameters,the composite layer was processed six times.During the processing,the thermal cycle of characteristic points and welding torque were monitored and recorded in real time,and the microstructure and Mechanical properties of the composite layer were characterized and analyzed.The results show that the variation of welding torque and characteristic temperature of FSP process test plate was affected by processing pass and reinforcement particles.After 4-pass of FSP macro-forming,the forming quality began to improve,and the forming quality of composite particles reinforced by single AIN particles was better than that of single ZrB2 and their combination · SEM results show that the reinforced phase particles break up after FSP,and there is particle aggregation in the back side.XRD results showed that the in-situ reaction between ZrB2,AIN and the matrix was not observed.Brittle fracture is the main fracture mode of the base metal with reinforced phase.After 6-pass of FSP,the tensile strength of the composite layer with single phase AIN reinforced particles decreases by 29.3%compared with that of the base metal.The lower elongation was found in ZrB2 single phase reinforced samples and micron ZrB2 and AIN hybrid reinforced samples with 50%ZrB2+50%AlN,all of which is about 11%.The hardness of reinforcing phase particle composites increases,but the hardness values fluctuate greatly in the adjacent positions.The wear mechanism of ZrB2 composite layer is the combination of abrasive wear and adhesive wear,while the wear of AIN composite layer is mainly abrasive wear and with less wear loss.