Artigo Revisado por pares

Fabrication of highly heterogeneous precipitate microstructure in an α/β titanium alloy

2024; Elsevier BV; Volume: 279; Linguagem: Inglês

10.1016/j.actamat.2024.120302

ISSN

1873-2453

Autores

Yandi Jia, Huhu Su, Shuo Cao, Rongpei Shi, Yingjie Ma, Qian Wang, Sensen Huang, Ruixue Zhang, Qing‐Miao Hu, Yufeng Zheng, Shijian Zheng, Jiafeng Lei, Rui Yang,

Tópico(s)

Bone Tissue Engineering Materials

Resumo

To obtain a synergistic combination of high strength and high ductility in titanium alloys, design and creation of heterogenous precipitate microstructure have attracted increasing attention. Herein, using Ti-3Al-5Mo-4.5V (wt.%, an α/β titanium alloy) as a model alloy, we demonstrated that a highly heterogenous α-phase precipitate microstructures with well-controlled length scale of spatial heterogeneity (i.e., micron-sized primary α and nano-scale secondary α precipitates), can be synthesized through activating the ω-assisted α nucleation transformation pathway that operates in metastable β titanium alloy alone. A detailed analysis of transformation pathway for ω phase and the underlying ω-assisted α nucleation mechanisms is carried out using the integrated advanced characterizations, theoretical calculations and simulations based on DFT, and phase-field modeling. Experimental results show unambiguously that the embryonic ω particles (also known as athermal ω) with partially collapsed structure are incapable of refining secondary α (αs). In contrast, the isothermal ω particles with a complete structural collapse play an important role in assisting αs nucleation, resulting in the formation of the ultrafine αs lamellae at nanoscales after two-step aging heat treatments. The contributions from the isothermal ω particles are then quantified using first-principles calculations and phase-field simulations. It is found that, even though the solute partitioning between a growing isothermal ω particle reduces the αs nucleation driving force in the surrounding β matrix, the elastic interaction between the ω particles and the αs nucleus provides more driving force for αs nucleation at specific locations of the ω/β interface. Our work extends the microstructure design strategy based on ω-assisted α nucleation mechanism from metastable β to α/β Ti-alloys, thereby significantly widening the application space of the strategy.

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