Effects of Ce and Mn on Microstructure and Mechanical Properties of Al-Cu Alloy

The microstructure and mechanical properties of Al-5Cu-0.6Mn-xCe（x=0.1, 0.3, 0.5, 0.7, 0.9） and Al-5Cu-0.3CeyMn（y=0, 0.6, 0.9） alloys were studied by OM, XRD, SEM and EDS. The results show that the microstructure of Al-5Cu-0.6 Mn alloy mainly consists of α（Al）, θ（Al₂ Cu）, Al₈Cu₄Ce and T(Al₁₂CuMn₂) phases with different Ce contents. After T5 heat treatment, the morphology and size of Al₈Cu₄Ce phase are little changed. The edges and corners of irregular block-like T(Al₁₂CuMn₂) phase are passivated. As the increase of Ce contents, the diffusion coefficient of Cu decreases, the number of θ（Al₂-Cu） phases that have not dissolved after T5 heat treatment is increased. The mechanical properties of heat-treated Al-5Cu-0.6Mn-xCe（x=0.1, 0.3, 0.5, 0.7, 0.9） alloys are increased at first and then decreased with the increase of Ce contents.When the Ce content is 0.3%, the mechanical properties reached the maximum values. The tensile strength is 306 MPa,yield strength is 124 MPa and elongation is 7%, which are increased by 54.5%, 40.9% and 40%, respectively, compared to that of the as-cast alloy. With the increase of Mn contents, the number of T(Al₁₂CuMn₂) phases in Al-5Cu-0.3Ce-yMn alloys is increased. The as-cast tensile strength and yield strength are increased at first and then decreased when Mn content increases from 0% to 0.9%. After T5 heat treatment, the mechanical properties decrease with the increase of Mn content.