Characterisation of heat-treated Ti-rich NiTi fabricated by laser powder bed fusion

¹ Laser Enabled Manufacturing, Photonics Center, Council for Scientific and Industrial Research, Meiring Naudè Road, Brummeria, Pretoria, 0184, South Africa.
² Centre for Materials Engineering, University of Cape Town, Library Rd, Cape Town, 7701, South Africa.
³ Department of Mechanical and Mechatronic Engineering, Stellenbosch University, Joubert street, Stellenbosch 7602, South Africa.
⁴ eNtsa, Nelson Mandela University, North campus, Gardham Avenue, Summerstrand, Gqeberha, South Africa.

Abstract

Nitinol (NiTi) is useful for biomedical applications, and laser-powder bed fusion (L-PBF) presents a unique opportunity to fabricate complex and patient-specific implant designs. The processing of nitinol via L-PBF, however presents a challenge as it results in an inhomogeneous microstructure that affects mechanical performance and can limit functional property performance. Moreover, an understanding of Ti-rich NiTi processed via L-PBF is lacking. Post-processing heat treatments are an avenue to alter and tailor the microstructure and thus influence the resulting phase transformations and mechanical performance. This paper presents various heat treatments and the influence of their resultant microstructures, phases and transformation temperature behaviour is characterised.