Systematic studies on structural instability in microscopic polycrystalline Ti-6Al-4V alloys subject to annealing via molecular dynamics

TL Yi, JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY, 39, 6409-6415 (2025).

DOI: 10.1007/s12206-025-2301-z

Ti-6Al-4V is a widely utilized metallic alloy known for its high strength-to-weight ratio, corrosion resistance, and stability at elevated temperatures. However, it exhibits limitations such as low ductility and wear resistance. Nanopolycrystalline structures, featuring nanoscale refined grains, offer potential improvements in mechanical strength, wear resistance, and fatigue performance. Thermal treatments, including annealing, are essential to enhance these properties. This study aims to understand the microscopic structural behavior underlying these macroscopic improvements. Two primary aspects are explored through molecular dynamics simulations: 1) Validation of inter- and intra-atomic potential models for titanium blocks with varying grain sizes by comparing simulated melting points with experimental data, and 2) Analysis of von Mises stress and local entropy variations in response to annealing. Results show that the Lindemann index profiles for titanium closely align with experimental melting points, validating the model's accuracy. In addition, bivariate histograms of local entropy and von Mises stress provide a means to differentiate material states based on annealing, with standard deviations of these parameters distinguishing between untreated and annealed configurations using the K-Mean clustering algorithm. This research offers fundamental insights into the behavior of nanopolycrystalline titanium alloys, advancing their characterization and potential applications in aerospace and biomedical engineering through molecular dynamics.

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