Formation mechanisms and control strategies of metallurgical defects and microstructures during laser powder bed fusion of AlSi10Mg lattice structures

Abstract

Lattice structures fabricated using laser powder bed fusion (LPBF) are pivotal for lightweight design. However, their small dimensions and intricate geometry intensify the likelihood of defect formation, such as lack of fusion (LOF), near-spherical pores, and microstructural coarsening. In this study, it was observed that the central region of lattice struts was especially susceptible to large-sized LOF in conjunction with the concave top surfaces due to frequent laser jumps. Furthermore, overheating during turnaround was identified as a contributor to excessive pores and surface bulging. Intriguingly, a unique layered melt mode emerged, characterized by coarse columnar grains exceeding 30 μm in size. A novel approach is proposed to reduce defects, refine grains, and enhance hardness during LPBF process, utilizing low laser power and a continuous scanning strategy. Using this manipulation strategy on typical lattice structures, porosity levels decreased by over 40 %. Ultimately, this research offers invaluable insights into refining printing conditions for lattice structures.