Grain boundary segregation and its implications regarding the formation of the grain boundary α phase in the metastable β-Titanium Ti–5Al–5Mo–5V–3Cr alloy

• Published in: Scripta materialia Vol. 207; p. 114320
• Main Authors: Prithiv, T. S., Kloenne, Zachary, Li, Dian, Shi, Rongpei, Zheng, Yufeng, Fraser, Hamish L., Gault, Baptiste, Antonov, Stoichko
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.01.2022
• Subjects: Atom probe tomography; Grain boundary segregation; Heterogeneous nucleation of phase transformations; precipitation; Titanium; Heterogeneous nucleation of phase transformations; Titanium; precipitation; Grain boundary segregation; Atom probe tomography
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/j.scriptamat.2021.114320

We investigated the origin of the deleterious grain boundary α phase formed during the aging of the β-titanium alloy, Ti–5Al–5Mo–5V–3Cr–0.5Fe (wt.%). We probed the composition of low and high-angle grain boundaries from the as-quenched β condition correlating electron microscopy and atom probe tomography. Our analysis reveals strong segregation of some α-stabilizing elements at both types of boundaries, especially oxygen, along with a depletion of β-stabilizing elements. The grain boundary maintains the body-centered-cubic structure despite the presence of this local composition. Our thermodynamic calculations, based on the measured grain boundary compositions, indicate that the segregation significantly increases the chemical driving force for α nucleation upon aging. Our work provides essential insight into the formation of the undesired grain boundary α layers along prior-β grain boundaries in metastable β-Ti alloys and paves the way for microstructural engineering of these alloys with enhanced mechanical properties. [Display omitted]