A metallurgical methodology has been set up in order to design alloys with improved mechanical properties such as strength–ductility trade-off, via improved strain hardening. To this end, a multi-concept approach including high-entropy alloys (HEAs), grain refinement, and chemical contrast and using the reversibility of the transformation-induced plasticity (TRIP) deformation mechanism has been implemented. The use of a conventional thermomechanical treatment involving cold rolling followed by an annealing stage at 650°C led to super-refined microstructures displaying an ultrafine-grained mixture (submicron size) of α (hcp) and β (bcc) phases. For Ti35Zr27.5Hf27.5Nb5Ta5 (Ti35-5-5), stress-induced martensitic transformation, and its subsequent reverse transformation during annealing at 650°C, led to a well-recrystallized state. A microstructure consisting of α and β equiaxed grains was obtained. Grain size is observed to increase within the submicron domain from about 300 to 600 nm with the holding time between 15 and 300 min. Contrariwise, for Ti35Zr26Hf26Nb6.5Ta6.5 (Ti35-6.5-6.5), which does not deform by the TRIP effect, the same thermomechanical treatment does not produce the recrystallization. Rather, precipitation of platelets in the recovered β matrix occurred. As for the mechanical properties, the yield strength of the alloys with dual-phase microstructure ranges between 950 and 1,150 MPa for Ti35-5-5 and between 850 and 950 MPa for Ti35-6.5-6.5, for annealing times ranging from 15 (higher yield strength) to 300 min (lower yield strength). This corresponds to a very large increase in the yield strength compared with that of the fully β alloys, displaying values of about 400 and 725 MPa for Ti35-5-5 and Ti35-6.5-6.5, respectively. Reasonable ductility was obtained for the alloys with optimized microstructures, which both display a tensile ductility of about 12% after annealing for 300 min at 650°C.

已经建立了一种冶金学方法，以通过改善应变硬化来设计具有改善的机械性能（例如强度与延展性的折衷方案）的合金。为此，已经实施了包括高熵合金（HEA），晶粒细化和化学对比以及利用相变诱导可塑性（TRIP）变形机理的可逆性的多概念方法。使用传统的热机械处理方法，包括冷轧，然后在650°C进行退火，可导致超细化的显微组织呈现出α（hcp）和β（bcc）相的超细颗粒混合物（亚微米尺寸）。对于Ti35Zr27.5Hf27.5Nb5Ta5（Ti35-5-5），应力诱导的马氏体相变及其随后在650°C退火期间的反向相变导致良好的重结晶状态。获得了由α和β等轴晶组成的显微组织。观察到晶粒尺寸在亚微米范围内从约300 nm增加到600 nm，保持时间为15至300 min。相反，对于不会因TRIP效应而变形的Ti35Zr26Hf26Nb6.5Ta6.5（Ti35-6.5-6.5），相同的热机械处理不会产生重结晶。相反，血小板在回收的β基质中沉淀。在机械性能方面，双相组织的合金的屈服强度对于Ti35-5-5为950至1,150 MPa，对于Ti35-6.5-6.5为850至950 MPa，退火时间为15（更高）屈服强度）至300分钟（较低的屈服强度）。与完全β合金相比，这对应于屈服强度的极大提高，Ti35-5-5和Ti35-6.5-6.5分别显示约400和725 MPa的值。对于具有优化的微观结构的合金，获得了合理的延展性，在650°C退火300分钟后，两者均显示出约12％的拉伸延展性。