Improving the mechanical properties of Al-5Si-1Cu-Mg aluminum alloy produced by laser additive manufacturing with post-process heat treatments

The thin-walled Al-5Si-1Cu-Mg aluminum alloy plate was fabricated by laser melting deposition additive manufacture technique followed by heat treatments. The microstructure and mechanical properties of the alloy are investigated considering the effects of solution/solution and artificial aging. Results show that due to the high cooling rate, a fine microstructure is formed with distinct grain structures and eutectic Si network embedded in the Al matrix, which gives rise to significantly better tensile properties (yield strength: 99 MPa, ultimate tensile strength: 223 MPa, elongation: 12.1%) as compared to as-cast Al-5Si-1Cu-Mg counterpart. After solution treatment, a superior ductility of approximately 22.4% can be achieved due to the increased mean distance and globularization of Si phases, and the appearance of nano-metric β'' and C phases during subsequent aging treatment gives a remarkable comprehensive mechanical behavior: The specimens show yield strength of 316 MPa, ultimate tensile strength of 416 MPa along with fracture strain of 15.2%. The combined effect of laser melting deposition and post-process heat treatments can yield parts with excellent mechanical properties, promoting the material for a wider range of applications.