Effects of rare earth elements on microstructure and tensile properties of Al-Si-Cu alloy at 250℃

The effects of rare earth elements (La,Sm) on the high-temperature (250 °C) microstructure and mechanical properties of Al-Si-Cu alloys were analyzed.The experimental results show that with the addition of La and Sm,the α-Al was significantly refined,and the eutectic Si changed from acicular to rod-like and granular.XRD and SEM analysis shows that the rare earth phases in the alloy were mainly AlSiRe and AlRe.Fracture morphology observations show the fracture mode of the alloy changes from brittle and ductile fracture to ductile fracture.With the increase of La or Sm contents,the mechanical properties of the alloys at 250 °C increase at first,and then decrease.When the contents of La and Sm are 0.4wt.% and 0.2wt.%,the tensile strength of the alloy reaches maximum of 143.91 MPa and 201.48 MPa,respectively.