Enhanced high-temperature stability in CuCrZrY alloys: reduced precipitate coarsening and recrystallization

Abstract

Precipitation strengthening is a critical strategy for developing high-performance Cu alloys that combine exceptional strength with high conductivity. However, this method often loses effectiveness at elevated temperatures due to the poor thermal stability of the precipitates, which tend to coarsen rapidly, leading to accelerated mechanical degradation. In this study, we introduce a CuCrZrY alloy that demonstrates remarkable structural and mechanical stability at high temperatures. Notably, after annealing at 550 °C for 500 h, only 18.8% of the grains were recrystallized. Through a combination of experimental investigations and first-principles calculations, we discovered that the strong solute-vacancy binding energy of Y in Cu significantly impedes bulk diffusion of solute, thereby inhibiting precipitate coarsening and recrystallization. The coarsening rate constant for the CuCrZrY alloy was found to be approximately half that of the CuCrZr alloy. During prolonged annealing, the formation of sub-grains via recovery enhances boundary diffusion, leading to a layered distribution of precipitates. The recrystallization model further elucidates the interplay between eutectic phases, precipitates, and the migration of recrystallization boundaries. Initially, eutectic phases contribute to the accumulation of geometrically necessary dislocations during rolling, which triggers recrystallization in the early stages of annealing. Additionally, the triple junctions of sub-grain and recrystallization boundaries facilitate precipitate coarsening, thereby reducing the pinning force. Consequently, the CuCrZrY alloy undergoes a unique recrystallization process characterized by discontinuous precipitate coarsening and a cycle of pinning-depinning-repinning of recrystallized grain boundaries. These insights provide valuable guidance for designing Cu alloys with stable microstructural and mechanical properties under prolonged high-temperature conditions.