Designing for Shape Memory in Additive Manufacturing of Cu–Al–Ni Shape Memory Alloy Processed by Laser Powder Bed Fusion

Abstract

Shape memory alloys (SMAs) are functional materials that are being applied in practically all industries, from aerospace to biomedical sectors, and at present the scientific and technologic communities are looking to gain the advantages offered by the new processing technologies of additive manufacturing (AM). However, the use of AM to produce functional materials, like SMAs, constitutes a real challenge due to the particularly well controlled microstructure required to exhibit the functional property of shape memory. In the present work, the design of the complete AM processing route, from powder atomization to laser powder bed fusion for AM and hot isostatic pressing (HIP), is approached for Cu–Al–Ni SMAs. The microstructure of the different processing states is characterized in relationship with the processing parameters. The thermal martensitic transformation, responsible for the functional properties, is analyzed in a comparative way for each one of the different processed samples. The present results demonstrate that a final post–processing thermal treatment to control the microstructure is crucial to obtain the expected functional properties. Finally, it is demonstrated that using the designed processing route of laser powder bed fusion followed by a post–processing HIP and a final specific thermal treatment, a satisfactory shape memory behavior can be obtained in Cu–Al–Ni SMAs, paving the road for further applications.

Processing of shape memory alloys research, applications and opportunities: a review

“…In most reports, NiTi shape memory alloy is discussed as a material that is suitable for a wide variety of useful applications [78].…”

Fe-Mn-Al-Ni Shape Memory Alloy Additively Manufactured via Laser Powder Bed Fusion

“…Therefore, the design of the experiment was conducted to cover all possible combinations of the significant procession parameters. The processing parameters design also depended on investigating the processing window of various alloys fabricated using LPBF including Cu-Al-Ni SMAs [52], Fe-Mn-Si SMAs [53], and NiTi SMAs [39].…”

Additive Manufacturing of Fe-Mn-Si-Based Shape Memory Alloys: State of the Art, Challenges and Opportunities

“…In parallel, additive manufacturing (AM) of metals emerged as a new paradigm of materials processing and has evolved very fast from prototyping to a real production technology in the recent years; see the reviews [35][36][37] for a general description of AM in metals and alloys. As an innovative fabrication process with short lead times, AM opens a new perspective to overcome constrains of conventional manufacturing in terms of complexity and to exploit the attractive functionalities of SMA, being already applied mainly to the production of TiNi [38][39][40], Cu-based [41][42][43] and Ni-Mn-based [44][45][46][47] SMA. In this context, research on the AM of Fe-based SMA has been only recently approached by laser powder bed fusion (LPBF) [48][49][50][51][52][53], laser metal deposition (LMD) [54] and wire arc (WAAM) [55], and the AM parameters must be still optimized in order to obtain the required microstructure to exhibit a good martensitic transformation on cycling, in order to guarantee the expected performances during shape memory and damping applications.…”