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

阐明了摩擦焊接条件和组成金属间化合物相的中间层对纯铝(A1)/纯镍（Ni）异种摩擦焊接接头在焊接状态和热处理状态下接头性能的影响。实验结果表明，无论摩擦压力和摩擦时间如何，焊接接头均在Al基体处断裂，而不是在接头界面处断裂。焊后热处理后，当层间宽度增加到约0.5mm以上时，接头抗拉强度急剧下降。由Al_3Ni、Al_3Ni_2、AlNi和A1M3组成的4种中间层数量最多出现在节理界面。当加热温度超过673K时，A1sNi2中间层生长最快，其计算自由能在4个中间层中最低。无论加热温度如何，断裂都发生在Al基体与中间层之间的界面处。当温度达到598K时，接头表面仍保持典型的韧性断裂模式，而当温度超过673K时，接头表面呈现脆性小面。详细计算得出Al基板接头界面周边残余应力为（93 ~ 127）MPa，认为这种高应力是导致接头热处理断裂的主要原因之一。

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.