Process-microstructure-properties of CuAlNi shape memory alloys fabricated by laser powder bed fusion

Abstract

Cu -based shape memory alloys (SMAs) show great potential in the application of high temperature, but their performance improvement combining with additive manufacturing is still challenging. In this paper, nearly defect-free (99.7% relative density) CuAlNi SMAs with two types of thermal-induced martensites, 18R and 2H, were successfully fabricated by laser powder bed fusion (LPBF). The remelting printing strategy with systematic optimization framework including densification and printability analysis was used to get optimal process window. The twin-related self-accommodation structure with long period stacking order substructure was formed during additive manufacturing process. The as-build samples show excellent mechanical properties (ultimate compressive strength of 1593 ± 10 MPa and large fracture strain of 23.0% ± 0.1%) with double-yielding, and outstanding shape memory effect, with maximum recoverable strain of 3.39% and nearly 100% recovery rate under compressive strain not exceeding 6%. Furthermore, the microstructural evolution in LPBF involving remelting, martensitic transformation, and 2H martensite was discussed. This result not only builds the microstructure framework involving high reflectivity alloys and martensitic transformation but also provides insight into the applicability of LPBF process in producing Cu-based SMAs.