Laser powder bed fusion for the fabrication of triply periodic minimal surface lattice structures: Synergistic macroscopic and microscopic optimization

The lightweight nature and superior mechanical properties of the triply periodic minimal surface (TPMS) structure have attracted considerable attention across various fields, including aerospace, automotive, and medicine. Currently, research on TPMS structures primarily focuses on optimizing macro-scale mechanical properties, with the limited investigation into macro/micro dual-scale optimization. This study introduces a novel nonlinear gradient TPMS structural design method, regulating the porosity of the TPMS structure through trigonometric functions, and designs Gyroid sin and Gyroid sin square structures. To fully tune the mechanical properties of the samples on both macro and micro scales, laser powder bed fusion (PBF-LB) and magnetic field (MF) were used to produce the structures. The effects of MF-assisted machining and annealing on the mechanical properties of Gyroid gradient structures were investigated by compression tests. The results show that the gradient specimens along the build direction have high energy absorption capacity and the gradient specimens perpendicular to the build direction have high elastic modulus. Annealing reduces the residual stresses and the MF refines the grains, which improve the mechanical properties of the structure. Additionally, after the addition of MF and subsequent annealing treatment, all structures show higher plateau stresses, and the energy absorption capacity of the structures along the gradient of the build direction is also improved.