Mechanical properties of AlSi10Mg alloy fabricated by laser melting deposition and improvements via heat treatment

Process optimization and heat treatment of AlSi10Mg aluminum alloy parts fabricated by laser melting deposition (LMD) based on coaxial powder feeding are conducted in this paper to improve manufacturing quality. The microstructures and mechanical properties of the LMD-built AlSi10Mg alloy parts are systematically investigated. Experimental results show the relative density of the block samples increase to 99.2% without larger pores and cracks after process optimization. The sample microstructures are found to display directional rapid solidification characteristics, with the Al-Si eutectic microstructure containing three microstructures being cellular, columnar dendrites and divergent dendrites. With solution and artificial aging heat treatments, Si atoms are rejected from the supersaturated Al matrix to form small Si granular particles. The heat treated samples display a uniform microstructure without heterogeneities and the microhardness remains stable at 118 HV. When the as-built sample is heat treated for solution time 2h, tensile strength increases from 292 MPa to 342 MPa due to the formation of strengthening phase Mg2Si.