Microstructure characterization of AlSi10Mg samples produced by Selective Laser Melting (SLM) technique was systematically investigated.Fine grain sizes of average 20 nm that resulted from the rapid solidification of the powder material were obtained.Under proper forming parameters,parts can attain a high relative density of 99.8% without cracks and pores on the surface.The microstructure of SLM specimens showed a network of Si dendrites across the surface of the Al matrix.To further improve the mechanical properties,conventional T6 heat treatment process was carried out.Precipitate phase with bulk shape was observed to be uniformly distributed in the heat treated sample which suggested an improvement to the vacancy intercalation energy of the sample.It was also observed that the T6 heat treatment improved the microstructural homogeneity.In addition,the interlayer boundary,a characteristic of SLM parts was entirely eliminated.The T6 heat treated AlSi10Mg SLM parts had an average hardness of 169 HV which is 37.4% improvement in hardness value compared to the untreated sample.