High-performance and lightweight shape memory alloys (SMAs) play a pivotal role in a variety of cutting-edge fields like aerospace, which however, are still quite difficult to be obtained until now. In the present work, we meticulously develop a novel lightweight Ti-12.5V-3.5Al-1Hf-0.8Fe-0.01B (at.%) SMA, which has a low mass density of ∼4.73 g/cm. Prominently, distinct from the conventional wisdom in previous studies that is mainly based on eliminating grain boundaries or developing desired texture, we utilize the grain refinement strategy introduced by elaborate thermal-mechanical training, which effectively enables us to achieve exceptional shape memory response and strength-ductility combination simultaneously. It was revealed that a dominant β phase structure is achieved in this newly designed fine-grain SMA, accompanied by some α″ variants penetrating the grain boundaries. Compared to the coarse-grained counterpart, the deformation process becomes more intricate, involving stress-induced martensitic transformation and additional reorientations, which ultimately results in an unusually large recoverable strain up to 9.3 %. Furthermore, the fine-grain structure also contributes to an enhanced specific yield strength up to ∼159 MPa·m³/kg, while maintaining a large tensile ductility of ∼30 %. In light of its impressive structure-function integration and cost efficiency, this new-type SMA would emerge as a promising candidate for various advanced lightweight applications in a broad spectrum of fields.

中文翻译：

---

晶粒细化在轻质钛合金中引起异常大的形状记忆效应

高性能、轻质形状记忆合金（SMA）在航空航天等各种尖端领域发挥着关键作用，但迄今为止仍很难获得。在目前的工作中，我们精心开发了一种新型轻质Ti-12.5V-3.5Al-1Hf-0.8Fe-0.01B（at.%）SMA，其质量密度较低，约为4.73 g/cm3。值得注意的是，与以往研究中主要基于消除晶界或开发所需织构的传统观点不同，我们利用通过精心的热机械训练引入的晶粒细化策略，这有效地使我们能够实现卓越的形状记忆响应和强度-同时具有延展性组合。据透露，在这种新设计的细晶 SMA 中实现了占主导地位的 β 相结构，并伴有一些穿透晶界的 α” 变体。与粗晶粒相比，变形过程变得更加复杂，涉及应力诱导的马氏体相变和额外的重新取向，最终导致高达 9.3% 的异常大的可恢复应变。此外，细晶粒结构还有助于将比屈服强度提高至~159 MPa·m3/kg，同时保持~30%的大拉伸延展性。鉴于其令人印象深刻的结构功能集成和成本效率，这种新型 SMA 将成为广泛领域中各种先进轻量化应用的有希望的候选者。