The twinning-induced plasticity (TWIP) effect contributes to high strength and ductility synergy in metastable β Ti alloys. Moreover, stress-induced α″ martensites (SIMs) are usually concurrent with TWIP, resulting in low yield strength. As a new pathway, the production of ω-strengthened metastable β Ti alloys from full α″ Ti alloys can be accomplished via reverse martensitic transformation. However, the deformation mechanisms of the metastable β Ti alloys acquired by this pathway have not been adequately reported. Accordingly, in this study, the full α″-type solution-treated (ST) samples of Ti-23Nb at.% alloy were annealed at 573 K followed by slow cooling to acquire the air-cooled (AC) and furnace-cooled (FC) samples with β phase and ω precipitates. Mechanical properties and deformation behaviors of these samples were systematically investigated. The AC and FC samples exhibited higher yield strengths than the ST samples. Although SIMs still existed in the AC samples, they were completely suppressed in the FC samples. The annealed samples demonstrated high ductility due to the TWIP effects stemming from {332}<113> twins. Furthermore, a distorted α″ phase exhibiting the abnormal orientation relationships (ORs) //<001>, {332}//{100}, and {110}//{110} with both β matrix and twin was revealed by high-resolution transmission electron microscopy and crystallographic analyses. These ORs were governed by the lattice distortion associated with a unique β matrix → distorted α″ → {332} twin pathway. This study suggests that metastable β Ti alloys with enhanced mechanical properties can be achieved via the α″ → β reverse martensitic transformation and ω precipitation.

中文翻译：

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通过逆马氏体转变开发具有孪生诱导塑性的 ω 强化 Ti-23Nb 合金


孪生诱导塑性 (TWIP) 效应有助于亚稳 β Ti 合金的高强度和延展性协同作用。此外，应力诱导的α”马氏体（SIM）通常与TWIP同时发生，导致屈服强度低。作为一种新途径，可以通过逆马氏体相变从全α”钛合金生产ω强化亚稳β钛合金。然而，通过该途径获得的亚稳态β Ti合金的变形机制尚未得到充分报道。因此，在本研究中，Ti-23Nb at.%合金的全α“型固溶处理（ST）样品在573 K下退火，然后缓慢冷却以获得空冷（AC）和炉冷（ FC) 具有 β 相和 ω 沉淀的样品。对这些样品的机械性能和变形行为进行了系统研究。 AC 和 FC 样品表现出比 ST 样品更高的屈服强度。尽管 SIM 仍然存在于 AC 样品中，但它们在 FC 样品中被完全抑制。由于 {332}<113> 孪晶产生的 TWIP 效应，退火样品表现出高延展性。此外，通过高分辨显示，扭曲的α“相表现出异常取向关系（OR）//<001>、{332}//{100}和{110}//{110}，同时具有β基体和孪晶。 -分辨率透射电子显微镜和晶体学分析。这些 OR 受到与独特的 β 矩阵 → 扭曲的 α” → {332} 孪生路径相关的晶格畸变的控制。这项研究表明，通过α”→β逆马氏体转变和ω沉淀可以实现具有增强机械性能的亚稳态β钛合金。