The effect of a remelting treatment scanning strategy on the surface morphology, defect reduction mechanism, and mechanical properties of a selective laser-melted Al-based alloy

Selective laser melting (SLM) technology is adopted to manufacture Al-based alloy in the fashion of zigzag scanning and island scanning, with a re-melted scanning treatment layer-by-layer. The surface morphology changes, defects reduction mechanism, and mechanical properties are investigated using Atomic force microscopy (AFM), Scanning electron microscope (SEM), Electron back-scattered diffraction (EBSD), X-ray diffraction (XRD), and iNano instrument. The re-melted scanning treatment provides enough incidental energy to retard the solidification rate and impact the inclusions. The melt viscosity decreases, and the pores left in the molten pool process have time to float and overflow. Due to the improvement of wettability and the reduction of defects, better interlayer bonding is achievable. The precipitated Mg2Si phase and crystal lattice distortion energy derived from the second heating treatment promotes the increase of Young's modulus, microhardness, and the ultimate tensile stress, to 93.56 GPa, 184.12 HV0.2, and 387 MPa, respectively. This work guides SLM-processed Al-based alloy with a more than adequate scanning-strategy selection.