Additive manufacturing of Cu-Al-Mn shape memory alloy with enhanced superelasticity

The Cu-based shape memory alloy (SMA) with highly oriented columnar crystals is an ideal candidate for the commercial application, especially the ones obtained through rapid cooling via additive manufacturing method. In this work, Cu₇₁Al₁₈Mn₁₁ (at%) shape memory alloy with strong <001> texture columnar grains was successfully prepared by selective laser melting (SLM). An L₂₇(3¹³) orthogonal array was designed to systematically investigate the effects of laser power, scanning speed, scanning spacing, layer thickness and their interactions on the forming quality of Cu₇₁Al₁₈Mn₁₁ alloys. Cu₇₁Al₁₈Mn₁₁ alloys with density of 7.3204 g·cm⁻³ and relative density of 99.18% were successfully prepared when the laser power, scanning speed, scanning distance and layer thickness were 240 W, 1000 mm·s⁻¹, 0.11 mm and 25 µm, the transformation onset temperature (M_s), martensite phase transformation termination temperature (M_f), austenite phase transformation onset temperature (A_s) and austenite phase transformation termination temperature (A_f) are −21.84, −26.04, −15.75 and −12.36 °C, respectively. The compression strength and fracture strain along the building direction (BD) were significantly superior to the scanning direction (SD), while the superelasticity of compression along the SD reached 2.50%, which was better than that of 2.32% along BD. The mechanical property and superelasticity anisotropy due to the formation of columnar grains and texture were discussed. This study shows that SLM is a proposed method for the preparation of Cu-Al-Mn SMAs with high superelasticity, which provides a new strategy for enhancing the shape memory alloy superelasticity.