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Aluminum alloys; Aluminum metallography; Chromium alloys; Chromium metallography; Cold rolling; Deformation; High resolution transmission electron microscopy; Metal cladding; Microstructure; Molybdenum alloys; Molybdenum metallography; Quenching; Scanning electron microscopy; Titanium alloys; Twinning; Vanadium alloys; Vanadium metallography, Alpha phase; Deformation twin; Nucleation sites; Omega particles; Phase present; Slow heating; Twin boundaries; Up-quenching, Titanium metallography
Abstract:
Hierarchical α microstructure in a metastable β Ti-5Al-5Mo-5V-3Cr (wt, Ti-5553) alloy has been investigated using scanning electron microscopy and transmission electron microscopy. Novel high-index 10 9 3}lt;3 3 1gt;β type deformation twins were characterized in the 10 cold-rolled Ti-5553. Without the pre-formed deformation twins, refined α microstructure and super-refined α microstructure were achieved in Ti-5553 using rapid up-quenching and slow heating treatment, respectively. On the contrary, with the pre-formed {10 9 3}lt;3 3 1gt; β deformation twins in the β matrix, hierarchical α microstructure was generated in Ti-5553, whether rapid up-quenching or slow heating treatment was adopted. It is observed that a layer of α phase precipitates from pre-formed {10 9 3}lt;3 3 1gt;β twin boundary and grows along the twin boundary. α sub-layers and fine-scale α precipitates form in the interior of pre-formed {10 9 3}lt;3 3 1gt;β twin. It is speculated that the large number of dislocations, metastable ω particles and α″ phase present as the substructure in the {10 9 3}lt;3 3 1gt;β twin may act as favorable nucleation sites for α sub-layers and fine-scale α precipitates. Thus, our work indicates that high-index {10 9 3lt;3 3 1gt;β twin may assist the formation of hierarchical α microstructure in the metastable β Ti-5553 alloy. © 2021, The Minerals, Metals Materials Society.
