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}<3 3 1>_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}<3 3 1> _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}<3 3 1>_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}<3 3 1>_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}<3 3 1>_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 3}<3 3 1>_β twin may assist the formation of hierarchical α microstructure in the metastable β Ti-5553 alloy.

已经使用扫描电子显微镜和透射电子显微镜研究了亚稳态 β Ti-5Al-5Mo-5V-3Cr（wt%，Ti-5553）合金中的分层 α 微观结构。新型高指数{10 9 3}<3 3 1> _β型变形孪晶在10%冷轧Ti-5553中得到表征。在没有预先形成的变形孪晶的情况下，Ti-5553 分别使用快速上淬火和缓慢加热处理获得了细化的 α 组织和超细化的 α 组织。相反，在β基体中预先形成{10 9 3}<3 3 1> _β形变孪晶，无论采用快速上淬火还是慢速加热处理，Ti-5553都会产生分层的α显微组织。观察到一层α相从预先形成的{10 9 3}<3 3 1>孪晶界并沿孪晶界生长。在预先形成的{10 9 3}<3 3 1> _β孪晶内部形成α亚层和细小α沉淀。据推测，{10 9 3}<3 3 1> _β孪晶中作为子结构存在的大量位错、亚稳态ω粒子和α″相可能是α子层和细尺度的有利成核位点。 α 沉淀。因此，我们的工作表明，高指数 {10 9 3}<3 3 1> _β孪晶可能有助于亚稳态 β Ti-5553 合金中分层 α 微观结构的形成。