The synergy of NiTi shape memory alloys and additive manufacturing: Applications and future directions

NiTi shape memory alloys are highly favored in engineering and biomedical realms owing to their unique responsiveness to environmental and external triggers. Laser powder bed fusion (LPBF) stands out as a premier method for additively manufacturing NiTi alloy, offering superior density, intricate geometric versatility, excellent surface finish, and chemical uniformity. This makes LPBF the preferred choice among various additive manufacturing (AM) techniques for NiTi alloy fabrication. The functional and mechanical properties of NiTi alloy are significantly influenced by the AM process parameters. Thus, understanding the interaction of these parameters is crucial for optimizing the final structures of additively manufactured NiTi components. However, the rapid melting and cooling rates inherent in the LPBF process can lead to elevated internal stresses, potentially resulting in issues such as cracking and nickel loss. These challenges can negatively impact the phase transformation temperature of the NiTi alloy. Despite these obstacles, studies in the literature demonstrate that LPBF-produced NiTi components exhibit functional and mechanical properties in line with American Society for Testing and Materials’ standards. As a result, they have found widespread use in biomedical applications, where their stress–strain hysteresis closely resembles that of bone tissues. Moreover, NiTi alloy’s remarkable actuation properties have made it indispensable in high-value engineering sectors such as automotive and aerospace industries. In essence, LPBF has emerged as a pivotal manufacturing technique for NiTi shape memory alloy, offering a pathway to produce components that meet stringent quality standards while unlocking a countless of applications across diverse industries. Despite existing challenges, the literature highlights the development of methods to fabricate NiTi components with the necessary shape memory and superelastic properties without postheat treatment, which can streamline production by lowering cycle time, cost, and duration, alongside research into how anisotropic microstructures impact alloy fatigue behavior under repeated actuations.