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

研究了纯铝（A1）/纯镍（Ni）异种金属摩擦焊接头在焊态和热处理状态下，摩擦焊接条件和由金属间化合物相组成的中间层对接头性能的影响。试验结果表明，无论摩擦压力和摩擦时间如何变化，焊接接头均在铝基体处断裂，而非接头界面处。焊后热处理后，当中间层宽度增加超过约0.5mm时，接头抗拉强度急剧下降。Al_3Ni、Al_3Ni_2、AlNi和AlM_3组成的四层中间层数量最多的位置在接头界面处。当加热温度超过673 K时，Al_（15）Ni_（2）中间层生长最快，其计算自由能在四个中间层中最低。无论加热温度如何，断裂均发生在Al基体与中间层的界面处。当接头加热到598 K时，表面仍保持典型的韧性断裂模式，而当接头加热到673 K时，表面显示出类似于小面的脆性。详细计算了拉伸状态下接头界面周边的残余应力为（93-127）MPa，认为这是热处理导致接头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.