Effect of lanthanum content on microstructure and mechanical properties of Al–5Mg–2Si-0.6Mn alloy in squeeze casting

Abstract

The effect of Lanthanum content on the microstructure and mechanical properties of Al–5Mg–2Si-0.6Mn alloy in squeeze casting was studied. The microstructure of the alloy was characterized by scanning electron microscope (SEM) and X-ray diffractometer (XRD). The mechanical properties of the alloy were tested by tensile testing machine. The results show that the rare earth Lanthanum has a significant effect on the secondary dendrite spacing and the volume fraction of α-Al + Mg2Si eutectic phase, both of which increase at first and then decrease with the increase of Lanthanum. When the content of Lanthanum is 0.05 wt.%, the maximum volume fraction of eutectic phase is 45.09%. When the content of Lanthanum is 0.05 wt.%, the minimum secondary dendrite spacing is 25.85 μm. When the addition of Lanthanum is more than 0.2 wt.%, the bulk LaAlSi phase is formed in the alloy, which is not coherent with the matrix, which reduces the mechanical properties of the alloy. When the addition of Lanthanum is 0.1 wt.%, the microstructure and mechanical properties of the alloy are the best. The ultimate tensile strength, yield strength and elongation of the alloy reached the maximum, which were 274 MPa, 197.2 MPa and 5.7%, respectively.