Influence of substrate plate heating on the properties of an additively manufactured Cu-Al-Ni-Mn shape-memory alloy

There is a major interest in Cu-based shape-memory alloys (SMAs) mainly due to their low cost and promising shape-memory properties. Yet, the applicability of these alloys is limited by their brittleness in the coarse-grained polycrystalline state, which is caused by a strong elastic anisotropy and the precipitation of intermetallic phases(a). Here, selective laser melting (SLM), an additive manufacturing technique, was used to tailor the phase formation and microstructure of the high-temperature shape-memory alloy Cu-11.85Al-3.2Ni-3Mn (wt.%)(b). The SLM process is capable of producing crack-free, fully martensitic samples with a reduced grain size, a high relative density of about 99% and transformation temperatures around 100°C. The focus of the present work is to utilize substrate plate heating for enhancing the transformation temperatures of directly fabricated specimens. In the first step, the substrate plate temperature was varied between 150 and 450°C in order to investigate the influence on the phase formation during SLM processing. The transformation behaviour can be correlated with the substrate plate temperature used during manufacturing and is compared with non-heated as well as conventionally annealed SLM samples. The use of substrate plate heating during selective laser melting of Cu-11.85Al-3.2Ni-3Mn proves to be a promising tool to prepare shape-memory parts with increased transformation temperatures without compromising the shape-memory behaviour, viz. pseudoelasticity, or the need of additional annealing steps.