Effects of laser rescanning on microstructure and mechanical properties of Al-10Si-1Mg alloy produced by laser-directed energy deposition

Laser-based additive manufacturing (AM) is a powerful tool for the production of complex metal parts. In this study, the Al-10Si-1Mg (wt%) alloy was fabricated using the laser-based directed energy deposition (L-DED) process. Additionally, the laser rescanning (LRS) process was used to fabricate samples under the same L-DED processing parameters. The microstructure and mechanical properties of the samples were investigated. Microstructural analysis showed the presence of a unique microstructure containing relatively coarse dendrites near the laser melt-pool boundary and fine equiaxed grains inside the melt pool. LRS was shown to effectively alter the grain size and texture of the alloy. Tensile tests in directions vertical and transverse to the L-DED BD showed that only the L-DED-processed alloys exhibited strong anisotropy in their mechanical properties. The LRS-processed samples exhibited significant improvements in strength and elongation with significantly reduced anisotropy compared to the L-DED-only processed samples. Under the same laser volumetric energy density conditions, increasing the laser scanning speed could effectively reduce the porosity, which resulted in a significant improvement in the mechanical properties with and without the LRS.