Additive manufacturing of Ti-Ni based ternary shape memory alloys

Metal additive manufacturing has become a powerful tool to develop customized metal alloys and to discover more advanced properties for novel extended applications. Ti-Ni based shape memory alloy is a group of intriguing smart functional materials, and adding a small amount of a third element can promote and induce more attractive functions. Due to the difficulty in traditional processing and the unique feature of material flexibility of in-situ alloying in additive manufacturing processes, not only Ti-Ni binary shape memory alloys but also Ti-Ni-X ternary shape memory alloys can be developed, manufactured, and investigated in-depth by additive manufacturing. This paper provides a brief review of the development of Ti-Ni based ternary shape memory alloys using metal additive manufacturing. The research status regarding a variety of Ti-Ni-X ternary alloys was summarized based on the classification of the two most widely used metal additive manufacturing processes: directed energy deposition and powder bed fusion. The main manufacturing issues were discussed and suggested, and the recommended research directions were made for future development.