This paper studies mechanical property and fractography of the welded joints obtained in different welding parameters such as welding heat and welding press with/without gas shield in TiNi shape memory alloy precise pulse resistance butt welding using tensile strength test, XRD, SEM and TEM measures. The optimum welding parameters obtaining high tensile strength welded joint are got. On the condition of welding press magneting current 2 A and welding heat 75%, the joint strength is the highest. This is important for to study other properties of TiNi shape memory alloy further. The experimental results state that argon gas shield have different effects on different welding parameters, less on welding press, but great on welding heat. But excessive welding press and welding heat have great effects on joint tensile strength. Too high welding heat can produce the new intermetallic compound, this intermetallic compound lead to dislocation density to increase and form the potential crack initiation, which can easily make the joint fracture under stress effect and decrease the shape memory ratio of joint for high density dislocation groups existing in the twinned martensite.
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