Effect of Mn and Mo on microstructure and mechanical properties of Al-Si-Cu-Mg-0.6Fe alloy

Abstract

Effect of different Mn and Mo contents on microstructure and mechanical properties of Al-Si-Cu-Mg-0.6Fe alloy was studied. Results indicate that the increase of Mo and decrease of Mn lead to a decrease in the size of the α-Al15(FeMnMo)3Si2 phase formed during solidification. The α-Al15(FeMnMo)3Si2 phase reaches a minimum value of about 16.3 μm at 0.2wt.% Mo and 0.1wt.% Mn addition. After solution treatment, the α-Al(FeMnMo)Si dispersed phase is precipitated. When only Mn is added, the α-Al(FeMnMo)Si dispersed phase mainly distributes near the grain boundaries, while when only Mo is added, it primarily distributes in the central region of the matrix. When both Mn and Mo are added, the dispersed phase has a larger and denser dispersed region and is uniformly distributed near the Al matrix and grain boundaries. Moreover, the best overall mechanical properties of the alloy are obtained with the combined addition of 0.1wt.% Mn and 0.2wt.% Mo, due to the smaller size of α-Al15(FeMnMo)3Si2 phase and the larger area fraction and higher density of the α-Al(FeMnMo)Si dispersed phase. The yield strength, ultimate tensile strength, and elongation are respectively improved 67.7 MPa, 48.5 MPa and 5.3%, respectively, compared to that of the alloy with only 0.3wt.% Mn.