Formation mechanism of W2Zr intermetallic compound by solid-phase interdiffusion

Abstract

The interdiffusion behavior between W and Zr, preferred orientation of the W₂Zr intermetallic as well as the underling mechanism were investigated. The W-Zr diffusion couple was annealing at 1300°C, 1400°C and 1500°C and then processing slow cooling and quenching respectively. The results indicated that the W₂Zr layer primarily grows toward the W side along the initial W/Zr interface, exhibiting a <111> preferred orientation. The growth direction is influenced by both the elemental concentration and atomic diffusion rates of W and Zr in the W₂Zr lattice. Zr diffusion towards W facilitates the W₂Zr formation as requiring the concentration condition of the intermetallic. Molecular dynamics simulations reveal that Zr diffuses faster than W in the W₂Zr lattice, further driving the W₂Zr layer growth towards W. Additionally, first-principle calculations of the diffusion energy barriers for the potential diffusion paths of W and Zr atoms in the W₂Zr lattice indicate that W atoms migrate along the <110> direction in the W₂Zr lattice, while Zr atoms transition along <111>. Consequently, Zr with a higher diffusion rate dominates the growth direction of W₂Zr, leading to a <111> preferred orientation. This study provides a novel perspective for analyzing the growth direction and the preferential orientation of intermetallic compound layers in reaction-diffusion systems.