Thermal diffusion and microstructural evolution of Cu-Zn binary system under hypergravity

It has long been a common assumption that the stress conditions for materials operating in hypergravity could be simplified to traditional stress conditions. However, such simplification has not been experimentally verified. In this study, we examined the thermal diffusion and microstructural evolution of the Cu-Zn binary system under hypergravity levels of up to 4700 g (g: gravity of Earth, 9.8 m/s2). Our findings revealed distinct differences when compared to the behaviour of the materials under traditional stress. Under hypergravity, we observed an enhancement in interfacial diffusion of atoms up to 3500 g, and this enhancement was suppressed under 4700 g hypergravity. Additionally, a directional effect was observed, where the diffusion layer formed in hypergravity from Cu to Zn direction was thicker than that formed under the opposite direction of hypergravity. Furthermore, the reduction of dislocations in the diffusion layer was observed as the hypergravity increased. The study suggests that the hypergravity-induced centrifugal force (Fg) and buoyancy force (Fb) significantly influence the diffusion characteristics of the Cu-Zn binary system. Fg enhances interfacial contact and promotes interfacial diffusion, while Fb promotes the diffusivity of vacancies, and thereby atoms, contributing to the observed directional effects. These factors ultimately lead to the formation of a biphasic phase and the suppression of precipitation under hypergravity. Additionally, as the hypergravity increases, defects/vacancies reduce, resulting in the suppression of diffusion. Our findings provide valuable insights into the diffusion and microstructural evolution of materials under hypergravity conditions.