Effects of Rare Earth La,Ce and Y on Microstructure and Mechanical Properties of Al-6.5Si-5.5Cu-0.2Zr-0.01Sr-0.06Ti-0.2RE Alloy

The effects of rare earth La,Ce and Y on the microstructure and mechanical properties of Al-6.5Si-5.5Cu-0.2Zr-0.01Sr-0.06Ti-0.2RE as-cast alloy were studied by SEM,OM,EDS and tensile test.The results show that the rare earth elements Ce and Y significantly improve the microstructure of the alloy,refine the α-Al phase,and improve the modification effect of the eutectic Si phase,while the improvement effect of La element is poor. The as cast alloys with rare earth elements Ce and Y have high mechanical properties,and the hardness is 76.8 HV and 79.05 HV,respectively,the tensile strength is 182.61 MPa and 216.83 MPa,and the elongation after fracture is 6.03%and 7.84%,respectively. The mechanical properties of the as-cast alloy with La element are lower,the hardness is 73.58 HV,the tensile strength is 160.58 MPa,and the elongation after fracture is 3.21%.The as-cast alloy with rare earth element La has better resistance to intergranular corrosion,smaller corrosion pits,maximum corrosion depth of 90 μm,and corrosion grade of three.However,the intergranular corrosion resistance of the as-cast alloys with rare earth elements Ce and Y gradually deteriorates,and the maximum corrosion depths are 110.21 μm and 145.68 μm,respectively.