Evolution of synthesis of FCC nanocrystalline solid solution and amorphous phase in the Ti-Ta based alloy by high milling energy

摘要

Pure Ti and Ti-based alloys exhibit two equilibrium phases: at lower temperatures they have a hexagonal close packed (alpha-Ti) crystalline structure while at higher temperatures they possess a body-centered cubic (beta-Ti) structure. However, in special conditions, they could exhibit a metastable face-centered cubic (gamma-Ti) crystalline structure. This paper aims to investigate the influence of Sn amount and milling time on the formation of gamma-Ti phase on the Ti-Ta based alloy. Four alloys with compositions Ti-13Ta-xSn (x: 3, 6, 9 and 12 at. %) were obtained by high energy milling. The alloys were analyzed by X-ray diffaction patterns, transmission and scanning electron microscopy. For the Ti-13Ta-3Sn alloy, the beta-Ti phase is formed in greater quantity, similar to 70% at 100 h. For the Ti-13Ta-6Sn and Ti-13Ta-9Sn alloys, the phase that is in greater quantity is gamma-Ti, around 100% at 100h. The Ti-13Ta-6Sn alloy shows a greater tendency to form the gamma-Ti phase, since the quantity is close to 100% at 50 h milling time. Thermodynamic calculations are comparable with experimental data. The calculations were made using the MAAT software based on Miedema's model. The MAAT is a free software that can be download from www.rpm.usm.cl. (C) 2020 Elsevier B.V. All rights reserved.