Grain boundary α-phase precipitation and coarsening: Comparing laser powder bed fusion with as-cast Ti-6Al-4V

• Published in: Scripta materialia Vol. 207; p. 114261
• Main Authors: Liu, Jianwen, Zhang, Kai, Yang, Yi, Wang, Hao, Zhu, Yuman, Huang, Aijun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.01.2022
• Subjects: Coarsening behavior; Electron backscattering diffraction; Grain boundary α-phase; Laser powder bed fusion; Titanium alloy; Titanium alloy; Laser powder bed fusion; Electron backscattering diffraction; Coarsening behavior; Grain boundary α-phase
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/j.scriptamat.2021.114261

Grain boundary α-phase (GB-α) precipitation and coarsening behavior in Ti-6Al-4V (Ti-64) processed by laser powder bed fusion (LPBF) were investigated and compared with those in as-cast Ti-64. GB-α in LPBF processed Ti-64 tended to precipitate at the triple junctions (TJs) of the β-phase grain boundaries during the subsequent annealing process. Kinetic analysis on GB-α showed that the coarsening mechanisms varied in LPBF processed Ti-64 at different annealing temperatures (bulk diffusion at 750 °C and interface reaction at both 850 and 950 °C), while were consistent in as-cast Ti-64 (interface reaction at all the three temperatures). The inconsistent coarsening mechanisms were attributed to the GB-α curvature difference caused by the different α lamellae nucleation mechanisms. These findings could help rationalize the GB-α morphology evolution and benefit the further mechanical property manipulation in LPBF processed titanium alloys. [Display omitted]