Elsevier

Scripta Materialia

Volume 207, 15 January 2022, 114320
Scripta Materialia

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

https://doi.org/10.1016/j.scriptamat.2021.114320Get rights and content

Abstract

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.

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Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

S.A. would like to acknowledge financial support from the Alexander von Humboldt Foundation. D.L. and Y.Z. would like to acknowledge the financial support by the startup funding from the University of Nevada Reno. The authors would like to acknowledge Prof. Dierk Raabe for the fruitful discussion. Christian Broß, Andreas Sturm, Uwe Tezins, Katja Angenendt and Monika Nellessen are thanked for their support of the APT, FIB, and SEM facilities at MPIE. This work was performed under the auspices of

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