Influence of laser mode on size effect in manufacturing AlSi10Mg mini-structures by laser powder bed fusion technology

Abstract

The mechanical properties of lightweight mini-truss structures manufactured by laser powder bed fusion (L-PBF) technology deviate widely from design targets. To investigate the causes and solutions of the above problems, the pillar diameter threshold that does not generate thermal accumulation under different laser modes was calculated by numerical simulation in this paper, which reveals the generation mechanism of thermal accumulation in the melting process of columnar samples. The effects of pillar diameter and laser mode on the microstructure and mechanical properties of AlSi10Mg prepared by L-PBF were also investigated experimentally. The experimental and simulation results show that in the continuous wave (CW) laser mode, as the diameter decreases, the solidification rate of the molten pool decreases, the size of the heat affected zone (HAZ) increases, and the ultimate tensile strength (UTS) and elongation after fracture (EL) decrease significantly. The microstructure of the submillimeter struts can be well modulated using a pulsed wave (PW) laser, and the sample strength can be increased by 12 %. The EL of the tensile samples in this study depended on the diameter of the sample, and there was no significant correlation with the laser mode. The experimental results regulate the size effect in additive manufacturing and improve the mechanical properties of metal mini-truss structures.