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Origin of the ductile-to-brittle transition of metastable β-titanium alloys: Self-hardening of ω-precipitates.
- Source :
-
Acta Materialia . May2019, Vol. 170, p187-204. 18p. - Publication Year :
- 2019
-
Abstract
- The ductile-to-brittle transition is commonly observed in metastable β -titanium (Ti) alloys containing ω -precipitates, while the fundamental understanding on ω -embrittlement hitherto remains elusive. In this work, the prototypical Ti-20 wt% Mo metastable β -Ti alloy has been systematically investigated by coupling experiments and first-principles calculation to eliminate this puzzle. It is shown that the structural evolution of ω -phase controls the deformation mechanism transition of twinning-to-slip in Ti Mo alloy, being the origin of ductile-to-brittle transition of this alloy. The initial trigonal ω -structure continuously collapses to hexagonal ω -structure (structural collapse) whilst Mo-atoms are rejected out concurrently (stoichiometric varieties), both leading to hardening of ω -precipitates. This self-hardening of ω -precipitates was further rationalized in terms of the enhanced propensity for a covalent character of the atomic bond demonstrated by the electronic density of states (DOS) from first-principles calculation. Specifically, the self-hardening behavior of ω -precipitates promotes dislocation slip on isolated planes in lieu of correlative slip on successive planes inside ω1 -variant, while dislocations are completely blocked ahead ω2/ω3/ω4- variants. This in turn renders the transition from deformation twinning that contributes to great macro-plasticity to ordinary dislocation slip that contributes to localized deformation bands in the present Ti Mo alloy. Image 1 [ABSTRACT FROM AUTHOR]
- Subjects :
- *ELECTRONIC density of states
*ALLOYS
*TITANIUM alloys
Subjects
Details
- Language :
- English
- ISSN :
- 13596454
- Volume :
- 170
- Database :
- Academic Search Index
- Journal :
- Acta Materialia
- Publication Type :
- Academic Journal
- Accession number :
- 136156174
- Full Text :
- https://doi.org/10.1016/j.actamat.2019.03.034