Revealing trace Si effect on precipitation behavior and properties of Cu-Cr-Zr alloy: Experiments and first-principles calculations

Abstract

High-performance Cu-Cr-Zr-X alloys are regarded as novel structural materials for nuclear fusion reactors. Through combining the experiments and density functional theory (DFT), the effect of Si addition on precipitation behavior and related properties of Cu-Cr-Zr-(Si) alloy was investigated for higher performance. Compared with the Si-free alloy, precipitation of Cr-rich phase is accelerated in the Cu-Cr-Zr-Si alloy (aging time<30 min at 450 °C). The partial radial distribution functions of the Cu-rich matrix reveal that the formation of Si-Cr clusters is resulted from the attractive Si-Cr binding energies at the nearest-neighbor distance. Moreover, the addition of Si can reduce the Cr migration energy in Cu. At the initial stage of aging at 550 °C, the precipitation kinetics is dominated by temperature. By TEM analysis, it is indicated that the growth of Cr-rich phase in Cu-Cr-Zr-Si alloy is delayed, which may be attributed to the decrease of Cu/Cr interface energy due to the addition of Si, as confirmed by first-principles calculations. The optimized performance of aged Cu-Cr-Zr-Si alloy can be achieved at 450 °C/4 h, and Orowan strengthening is dominant. This work can provide a guideline for design of novel high-performance Cu-Cr-Zr-X alloys.