The Research Of Plasma Welding On Cu-Zn-Al Shape Memory Alloy

In this paper, do the Cu-Zn-Al shape memory alloys welding with the high energy plasma beam melt and push welding method, and research the welding method, the welding technics, the welding quality and the welding heat treatment. The primary content research is divided in the following parts:The welding quality of copper and copper alloy is analyzed and the high-energy plasma beam testing equipment system is improved. Special fixture in the testing system is designed according to the features of resistance welding. In the welding, the preloading spring force would be all or partly squeezed out by the melting weld metal, and this can reduce the width of heat-affected zone and improve the state of grain as far as possible to improve the quality of their joints.About this welding process, the protective gas and the nozzle distance are studied; the affects of welding current, time, the hydronium gas flux to the welding performance of Cu-Zn-Al shape memory alloy are studied. And the primary technics parameters are confirmed.According to analyse of heat treatment texts and the X-Ray Diffraction text of the welding joints, the heat treatment technology that is required to the memory function of the testing materials is confirmed.The tensile strength, phase transition point,component and shape memory properties of original alloy wire and welding joints after heat treatment are studied.The phenomena that the welding joints stress- induced martensite phase transformation is studied and it is concluded in the following parts:the critical stresses that induce martensite phase transformation increases with the increase of temperature; its Pseudo-Elasticity is nonlinear;with the mechanical cycle increases the residual displacement will increase, the hysteresis area will reduce and the phenomena that stress induced the martensite phase transition will gradually disappear, or cause fatigue failure to the material.