Microstructure and strength of selectively laser melted AlSi10Mg

Samples of laser powder bed processed AlSi10Mg have been examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning TEM so that the complex microstructures of as-fabricated samples could be characterised. In longitudinal sections, columnar Al grains, about 10 mu m in diameter, dominate the microstructure, but some equiaxed regions are seen. The columnar grains are made up of long cells, about 500 nm in width, rather than dendrites, which are separated from adjacent identical orientation long cells and from non-parallel cells at Al grain boundaries, by Al-Si eutectic. There is a substructure on the scale of 300-500 nm, of identical orientation "sub cells" throughout the length of the long cells also separated by regions of the Al-Si eutectic. Micro diffraction is necessary to distinguish between cell boundaries, sub-cell boundaries and grain boundaries. The "cell-like" structures observed in cross section samples are cross sections of these long cells and of the Al-Si eutectic at cell boundaries. Deformed as-fabricated samples have been examined in TEM to assess the role of Si particles within the cells and of the Al-Si-eutectic boundaries on the response of SLMed samples to plastic deformation. In addition in situ compression tests in a TEM have been carried out which show that cell boundaries, sub-cell boundaries and particles within the cells limit dislocation movement during deformation. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.