Similar and Dissimilar Joining of Nitinol Through Transient Liquid Phase Bonding

Nitinol, a near-equiatomic nickel-titanium alloy, is one of the most widely used shape memory alloys (SMAs) due to its excellent mechanical behavior, corrosion resistance, and large recoverable strain limit (~8%)¹. For these reasons, nitinol has been fielded in many aerospace applications, including self-deploying actuators, folding aircraft wings, and rover tires². However, these applications require joining nitinol to support structures which are often a different alloy class. Traditional welding methods, when applied to nitinol, lead to the formation of brittle intermetallic phases, reduced strength within the joint region, and decreased functional performance (such as recoverable strain and heterogeneous transformation temperatures)³. Thus, dissimilar joining of nitinol remains a grand challenge in the ultimate use of these materials, and advances in joining technologies will greatly expand the potential applications of SMAs.