Regulation of athermal ω formation by one-dimensional chemical ordering in Zr-10% Nb alloys

ZS Li and HJ Li and L Zhao and HX Zong and XD Ding and T Lookman and J Sun, PHYSICAL REVIEW MATERIALS, 9, 083605 (2025).

DOI: 10.1103/nrf7-3m94

The formation of w phase severely impairs the mechanical properties of metastable f-Ti and f-Zr alloys, causing embrittlement and loss of ductility, yet its transformation kinetics remain poorly understood. Using molecular dynamics simulations, we examine how chemical ordering influences the f-*w phase transformation in Zr-Nb alloys. Our results reveal that the nucleation of the w-phase is influenced not only by the concentration of alloying elements, but also by the degree of chemical ordering along (111)beta directions, with Nb atoms occupying two out of every three 111f planes. Notably, in rapidly quenched Zr-10%Nb alloys, enhanced local chemical ordering leads to larger w precipitates with their crystallographic orientation directed by the (111)beta ordering of Nb atoms. This interaction results in nanosized, morphologically distinct athermal w phases, facilitated by local (111)beta ordering. The propensity for w-phase formation in chemically ordered regions arises from a reduced shear modulus and lower transformation barriers. These insights provide valuable guidance for understanding microstructural control in developing high-performance titanium and zirconium alloys.

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