Mechanical Response and Superelastic Properties of Cu-11.85Al-3.2Mn-0.1Ti TPMS Structures Printed by Laser Powder Bed Fusion

Abstract Triply periodic minimal surfaces (TPMS) are structures with smooth surfaces and excellent energy absorption properties. Combining new functional materials, such as shape memory alloys, with TPMS structures provides a novel and promising research field. In this study, three TPMS structures (Gyroid, Diamond, and Primitive) of Cu-11.85Al-3.2Mn-0.1Ti alloy were printed by laser powder bed fusion, which is favorable for the fabrication of complex structures. The manufacturing fidelity, mechanical response, and superelastic properties of the three structures were investigated. Stress distributions in the three structures during compression were analyzed by finite element (FE) simulation. The three structures were equipped with high-quality, glossy surfaces and uniform pores. However, due to powder adhesion and forming steps, there were volumetric errors and dimensional deviations between the samples and the CAD models. The errors were within 1.6% for the Gyroid and Diamond structures. The dimensional deviations at the nodes in the three structures were less than 0.09 mm. The microstructures of all structures were β1´ martensite, consistent with the cubic sample. Experimental results of compression showed that the structures underwent a layer-by-layer compression failure mode, and the Primitive structures exhibited a more pronounced oscillatory process. The Diamond structures showed the highest first fracture stress and strain of 164.67 MPa and 13.89%, respectively. It also possessed the lowest yield strength (61.97 MPa) and the best energy absorption properties (7.6 MJ/m3). Through the deformation analysis, the Gyroid and Diamond structures were found to fracture at a 45° direction, while the Primitive structures fractured horizontally. These findings were consistent with the results obtained from the FE simulation, which showed equivalent stress distributions. After applying various pre-strains, the Diamond structures displayed the highest superelastic strain of up to 3.53%. The superelastic recovery of all samples ranged from 63.5% to 71.5%.