Tailoring the Superelastic Properties of an Additively Manufactured Cu-Al-Mn Shape Memory Alloy Via Adjusting the Scanning Strategy

The effects of the scan vector rotation angle in adjacent layers during laser powder bed fusion of a Cu71.6Al17Mn11.4 (at.%) shape memory alloy on the porosity, microstructure, transformation temperatures, as well as superelastic properties, were investigated. To explore the influence of the applied scanning strategy, a bidirectional stripe hatching was employed by utilizing 0°, 25°, 50°, 79° and 90° rotation of the scanning direction in adjacent layers. Changing the scan vector rotation had no apparent effect on the characteristics of porosity. The scan vector rotation allowed a manipulation of the microstructure (grain size, texture) to some extent which was evaluated via electron backscattered diffraction (EBSD) analysis. While the size and distribution of grains only showed negligible differences, a more pronounced change in the texture as well as in the grain misorientation has been observed. A significant recoverable strain difference for the applied scan vector rotations was observed as a result of compressive loading-unloading tests. The samples produced with 90° scan vector rotation exhibited 6.05% recoverable strain under 8% applied strain, whereas only minor recoverable strain values (around 1.4%) were obtained in the specimens produced without a shift in the scan vector rotation (0°). Other vector rotations (25°, 50°, 79°) resulted in a moderate superelastic performance with respect to the 90°-samples. These findings clearly show that polycrystalline Cu–Al–Mn shape memory parts with high shape-recovery rates can be directly fabricated using laser powder bed fusion and an adjusted scanning strategy. Thus, this approach can serve as a general tool to optimize or control superelasticity in additively manufactured Cu-based SMAs.