Annealing behavior of AlSi10Mg alloy fabricated by laser powder bed fusion

Abstract

The AlSi10Mg alloy fabricated by laser powder bed fusion was subjected to isochronal annealing for 2h at temperatures in the range of 100–520 °C. Recovery and grain growth of the annealed samples were investigated by combining EBSD and in situ TEM techniques. A bimodal grain size distribution with grain sizes of 0.9 μm and 2.3 μm was developed in the initial sample, where large grains were found in the interiors of melt pools and most of small grains were distributed along melt pool boundaries. In-situ TEM investigations revealed that nucleation that occurs at the melt pool boundaries is as a consequence of migration of high angle boundaries during annealing. A slight increase in grain sizes was discovered during high-temperature heat treatment, indicating the remarkable thermal stability of the alloy compared to conventional cast Al-Si alloys. This is explained by the fact that the stable eutectic Si structure, which was originally formed during rapid solidification, can effectively retard grain boundary migration during recrystallization.