A Novel Optimization Approach for Additively Manufactured Niti Alloys with Superior Compressive Strength and Recoverability

NiTi alloys fabricated by laser powder bed fusion (LPBF) have gained widespread attention and use because of their flexible design for complex structures with excellent superelasticity. However, the optimization of processing parameters has traditionally been stepwise and the performance at different temperatures needs be evaluated further. In this paper, four-factor and five-level orthogonal experiments were designed to optimize the processing parameters within a large process window. In addition, the compressive performance at various temperatures (16, 36, 56 and 76 °C) was evaluated to determine the superelasticity of LPBF-NiTi alloy printed with optimized processing parameters. The LPBF-NiTi alloy exhibited a superior fracture strain and stress (0.497 and 3435 MPa, respectively) at 56 °C. In the first loading/unloading compressive test, the recoverable strain decreased from 0.108 to 0.081 as the temperature increased from 16 to 76 °C. As cyclic loading and unloading progresses, the stable recoverable strain decreased from 0.083 to 0.073. The superior compressive strength and stable recoverability were achieved by combining high relative density (99.98 ± 0.01%) and hardness (238 ± 4 HV1) in determining the optimized parameters within a large processing window. This research fabricated a highly dense, high-performance LPBF-NiTi alloy through multifactorial and multilevel process parameter optimization, providing guidance for NiTi alloy application.