Effect of common alloying elements on α’ martensite start temperature in titanium alloys

Abstract

Accurate prediction of the martensitic start (Ms) temperature is critical for controlling the β to α′ phase transformation process in titanium alloys. Based on the Galindo-Nava's model, the changes in Ms temperature for common Ti-X binary titanium alloys and Ti–Al–V–O systems with varying contents of alloying elements have been predicted in this work. The main results are as follows: The profiles of Ms and Tβ are consistent for different alloying elements, and the difference between Ms and Tβ is larger for alloying elements with higher substitutional strain energy. As the α phase stabilizing element content increases, the Ms point of the alloy raises, while it decreases for increasing β phase stabilizing element. Moreover, the effect of Al on Ms is stronger compared to that of V. It is worth mentioning that the metastability of the β phase at high temperature is the main factor determining Ms. Additionally, the substitutional strain energy contributed by Al is about two orders of magnitude higher than that of V, or the interstitial strain energy of (per 0.05 wt%) O. The present calculations are in good agreement with certain experimental results. The findings provide valuable insights into understanding and controlling the process of β to α′ phase transformation, and they would offer guidance for component design and optimization of titanium alloys.

Keywords

• Martensitic phase transformation
• Thermodynamics
• Elastic strain energy
• Titanium alloys