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Microstructure and Properties of Alsi10mg Fabricated by Selective Laser Melting (SLM)
P.K. Bai, Z.Y. Zhao, J. Li, L.Y. Wu, M.J. Liang, L. Tan and H.H. Liao

The microstructure and mechanical properties of overlapping and nonoverlapping areas of AlSi10Mg samples fabricated by selective laser melting (SLM) were investigated. The results showed that the columnar grains with a mean size of 0.8 μm, which grew epitaxially perpendicular to the boundary of the meltpool, dominated the microstructure in the meltpool. The inside of the overlapping area was mainly cellular dendrites, with an average diameter of 1.5 μm and different orientations. The finer fibrous eutectic Si phase was well distributed in the meltpool, the microhardness was 5.2% higher than that in the overlapping area, and the track-track overlapping area was the main area that gave rise to the formation of initial cracks when the sample was compressed. The reason for this phenomenon is that in the meltpool, the fibrous eutectic Si phase is finely dispersed, and the grain size is small, resulting in greater hardness than in the overlapping area. In the overlapping area, the distribution of the Si phase was heterogeneous, and the grain orientation was different in the adjacent region. When compression was applied, the force could not be uniformly dispersed, and this resulted in cracks. The loading direction of the force was perpendicular to the growth direction, and the slip surface direction of the overlapping area was parallel to the direction of the applied force; therefore, the crack initiation occurred mainly in the track-track overlapping area.

Keywords: Fibre laser, AlSi10Mg alloy, selective laser melting (SLM), microstructure, microhardness

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