Effect of V on high-temperature mechanical properties of Al-5Cu-1.5Ni alloy

The effects of V on microstructure, room temperature, and high-temperature (350 degrees C) mechanical properties of Al-5Cu-1.5Ni alloy were investigated. The results show that Al-5Cu-1.5Ni-xV alloys mainly comprise alpha-Al, Al2Cu, Al-3(Ni, Cu)(2), Al3Ni, Al7Cu4Ni, and Al10V phases. The addition of V can signally refine alpha-Al dendritic structure, which improves the mechanical properties of the as-cast alloys at room and high temperatures. After T6 heat treatment (540 degrees C/12 h/WC +170 degrees C/8 h/AC), alpha-Al, network skeleton structure Al-3(Ni, Cu)(2), and Al10V phases all show coarsening, while the fine nano-theta '-Al2Cu precipitated from the matrix and dispersed distributed. The introduction of V promotes the quantity of precipitated theta '-Al2Cu particles. The ultimate tensile strength of the heat-treated alloys at room and high temperatures is greatly improved compared to that of the as-cast alloy. The highest high-temperature ultimate tensile strength of the alloys with V is 111.8 MPa, 21.5% higher than that of the base alloy. The analysis shows that the improvement of high-temperature mechanical properties after heat treatment is mainly due to the introduction of V, increasing the precipitated quantity of nano-theta '-Al2Cu particles and improving its thermal stability. The dispersion strengthening effect of theta '-Al2Cu particles exceeds the weakening effect of other adverse microstructures on the mechanical properties.