Effect of ultrasonic spot welding on the mechanical behaviour of NiTi shape memory alloys

Abstract

NiTi shape memory alloy joints were obtained using ultrasonic spot welding and the effect of this manufacturing process on the mechanical behaviour was investigated. Comparing to the as-received NiTi, the welded material presented increasing austenite transformation temperatures and decreasing martensite finish transformation temperatures. No detrimental intermetallic compounds were found at the weld interface due to the advantages of this solid-state welding technology. A typical interfacial fracture mode was observed at the fracture surface with numerous cleavage planes and micro cracks. Additionally, plastically deformed regions were observed in the weld spot. Ultrasonic welding can be used to effectively join NiTi shape memory alloys.