The microstructure and mechanical properties of friction welded joints of Al-Cu alloy matrix composite and Al-Si- Cu-Mg alloy castigns

摘要

Microstructures, Vickers hardness, tensileproperties and rotated beam fatigue properties of friction weldedaluminum-borate whisker reinforced Al-Cu alloy matrixcomposites (MMC) joints with Al-Si-Cu-Mg alloy (C355)castings were examined. The mixed layer of MMC and C355 isformed near the bonding interface by the shear stress during therotated friction period. This layer has different composition fromboth Al-Cu alloy and Al-Si-Cu-Mg alloy, and the mixed layer haslower strength but also has a role to relax thermal stress duringwaterquenching after solution treatment. Softening occurs near thebonding interface and the joints have lower tensile properties thanthose of C355 alloy castings in as-friction welded joints. After T6heat treatment, hardness of the joint is recovered and the joint hashigher tensile and fatigue properties than those of C355-T6 alloycastings. It is concluded that a combination of the friction weldingand post-weld T6 heat treatment is a reliable method to assuregood performance for MMC/C355 joints.