Atomistic insight into the effects of solute and pressure on phase transformation in titanium alloys

TL;DR

This study uses density functional theory to analyze how solutes and pressure influence phase transformations in titanium alloys, revealing mechanisms to enhance their stability and mechanical properties.

Contribution

It provides new atomistic insights into how solute elements and external pressure synergistically affect phase transformation barriers in Ti alloys.

Findings

Both alloying and pressure lower transformation barriers.

Al and Mo are most effective at ambient conditions.

Solute and pressure effects modify electronic structure and bonding.

Abstract

The phase stability and transformation between hexagonal close-packed (hcp) {\alpha}-phase and body-centered cubic (bcc) \b{eta}-phase in titanium (Ti) alloys are critical to their mechanical properties and manufacturing processes for engineering applications. However, many factors, both intrinsic and extrinsic (e.g., solute elements and external pressures, respectively), may govern their phase transformations dynamically, which is crucial to the design of new Ti alloys with desirable properties. In this work, we study the effects of various solute elements and external hydrostatic pressures on the solid-state phase transformations in Ti alloys using density functional theory (DFT) and nudged elastic band (NEB) calculations. The results show that both alloying and applied pressure reduce transformation barriers, with Al and Mo being most effective under ambient conditions, while Nb, V, Zr, and Sn show enhanced transformation kinetics under stress. Solute-induced modifications to the local electronic structure and bonding environment, particularly under pressure, contribute to variations in phase stability. We identify a synergistic interaction between solute effects and external stress, which facilitates phase transitions that are unachievable under static conditions. These findings provide atomistic insights into the coupled chemical-mechanical mechanisms underlying phase transformations in Ti alloys with improved phase stability and mechanical performance.