Development of an Interatomic Potential for the Simulation of Defects, Plasticity and Phase Transformations in Titanium

TL;DR

This paper introduces new interatomic potentials for titanium that accurately simulate defects, plasticity, and phase transformations, using advanced methods to determine phase transition temperatures and address temperature-dependent behaviors.

Contribution

The authors develop and validate multiple embedded atom potentials for Ti, including a temperature-dependent model, to improve simulation accuracy across different phases and conditions.

Findings

The Ti1 potential accurately reproduces hcp-bcc transformation and melting temperatures.

Ti2 and Ti3 potentials effectively model defect properties and plasticity.

A combined temperature-dependent potential enhances simulation versatility.

Abstract

New interatomic potentials describing defects, plasticity and high temperature phase transitions for Ti are presented. Fitting the martensitic hcp-bcc phase transformation temperature requires an efficient and accurate method to determine it. We apply a molecular dynamics (MD) method based on determination of the melting temperature of competing solid phases, and Gibbs-Helmholtz integration, and a lattice-switch Monte Carlo method (LSMC): these agree on the hcp-bcc transformation temperatures to within 2 K. We were able to develop embedded atom potentials which give a good fit to either low or high temperature data, but not both. The first developed potential (Ti1) reproduces the hcp-bcc transformation and melting temperatures and is suitable for the simulation of phase transitions and bcc Ti. Two other potentials (Ti2 and Ti3) correctly describe defect properties, and can be used to simulate plasticity or radiation damage in hcp Ti. The fact that a single EAM potential cannot describe both low and high temperature phases may be attributed to neglect of electronic degrees of freedom, notably bcc has a much higher electronic entropy. A temperature-dependent potential obtained from the combination of potentials Ti1 and Ti2 may be used to simulate Ti properties at any temperature.