Effects of individual and combined additions of transition elements (Zr, Ti and V) on the microstructure stability and elevated-temperature properties of Al–Cu 224 cast alloys

Abstract

The effects of individual and combined additions of transition elements (TEs) Zr, Ti, and V on the microstructure evolution and elevated-temperature mechanical and creep properties of Al–Cu 224 cast alloys were investigated. All alloys had a mixed precipitate microstructure of θʺ- and θʹ-Al2Cu after T7 heat treatment. During the thermal exposure at 300 °C, θʺ transferred into θʹ as the predominant strengthening phase. The coarsening resistance of θʹ during the thermal exposure and further creep deformation was greatly improved by the addition of TEs. Individually, Zr addition demonstrated the best efficiency in stabilizing θʹ, while the combination of Zr + V and Ti + Zr + V achieved the highest efficiency. The addition of TEs generally improved the yield strength (YS) at 300 °C, and the ZrV and TiZrV alloys achieved the highest YS. A close correlation between the YS and the distribution and thermal stability of θʹ was observed. The creep resistance at elevated temperatures was affected by the thermal stability of θʹ and grain size. Zr-containing alloys (ZrV, Zr, and TiZrV) exhibit superior creep resistance. In terms of comprehensive properties, the combined addition of TiZrV alloy exhibited the best elevated-temperature performance.