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The ordered γ′-(Ni, Cu)3Al is a crucial strengthening phase that improves the high-temperature resistance of Cu-based alloys, so it is important to predict the kinetic evolution of the composition and microstructure of the phase for high-temperature applications. Herein, this paper discusses the temporal evolution of the composition and coarsening of the γ′ phase in a model ternary Cu50Ni37.5Al12.5 (at%) alloy during isothermal aging at 600, 700, 800, and 900 °C for 1–36 h. It is found that the γ′ phase composition evolves linearly toward a binary γ′ phase as the aging time increases during the process of aging at 800 and 900 °C, which cannot be predicted by the ternary phase diagrams alone. Meanwhile, through the utilization of the aforementioned linear law, the γ phase composition can be predicted at a given temperature within the alloy by determining the volume fraction of the γ′ phase. Additionally, the activation energy for coarsening decreases, and the coarsening rate of the γ′ phase increases owing to the higher diffusion rate of Cu at high temperatures. The addition of microalloying elements with strong enthalpic interactions is beneficial for reinforcing the structural stability of the γ′ phase. This work provides a simple method for the compositional analysis and performance prediction of Cu–Ni–Al alloys at elevated temperatures and sheds light on the subsequent compositional design and optimization of Cu-based high-temperature alloys. [ABSTRACT FROM AUTHOR]

Mg-Zn-Zr wrought alloys have been widely developed for lightweight applications. Zr microalloying contributes to remarkable grain refinement during solidification and bimodal microstructure via forging. To obtain an optimum Zr content for a balance between cost and mechanical property, it is necessary to understand the influence of varied Zr addition levels on the microstructure and mechanical property of the final forged product. In the present study, two levels of Zr addition (nominally 0.40 wt.% and 0.60 wt.%) were added to a Mg-3 wt.% Zn alloy to investigate the effect of varied Zr contents on the microstructures under as-cast, as-forged and tensile-strained conditions, as well as the uniaxial tensile properties of the as-forged alloy. The as-forged microstructures comprise fine dynamic recrystallized (DRXed) grains and coarse deformed (unDRXed) domains, which become more refined with the Zr content increasing from ~ 0.43 wt.% to ~ 0.67 wt.%. The microstructural change caused by the increased Zr addition has minor impact on 0.2% proof stress but remarkably improves both uniform and post-uniform elongations, for which the underlying mechanisms have been discussed. [ABSTRACT FROM AUTHOR]