INTERLAYER GROWTH AND SIMULATION OF JOINT STRENGTH OF DISSIMILAR METAL JOINT INTERFACE

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It was clarified how friction welding condition and interlayers composing with intermetallic compound phases affect the joint properties of pure aluminium(A1)/pure nickel(Ni) dissimilar friction welding joint in as-welded and heat treated conditions. The experimental results indicated that all as-welded joints fractured at Al substrate, not joint interface, in spite of friction pressure and friction time. After post-weld heat treatment, the joint tensile strength drastically dropped when the interlayer width increased more than approximately 0.5mm. The maximum number of four interlayers composing with Al_3Ni, Al_3Ni_2, AlNi and A1M3 occurred at joint interface. A1sNi2 interlayer grew fastest when the heating temperature exceeded more than 673K, and its calculated free energy was lowest in four interlayers. The fracture occurred at the interface between Al substrate and interlayers regardless of heating temperature. While the surfaces remained typical ductile fractured pattern for the joint heated up to 598K, they revealed brittle like facet for the joint heated more than 673K. Detail calculated residual stresses at the periphery of the joint interface of Al substrate were (93-127)MPa in tension, and this high stress was thought as one major reason that generate the joint fracture by heat treatment.