难熔金属及合金的蠕变性能研究进展

The progress research of creep property in refractory metals and alloys

摘要:

本文系统综述了难熔金属（W、Mo、Ta、Nb）及其合金、难熔高/中熵合金的蠕变性能与核心机理。蠕变作为高温恒定应力下的缓慢塑性变形，其行为由同系温度（TH）调控，TH<0.3 时以位错滑移为主，0.30.5 呈现三阶段蠕变，扩散作用随温度升高愈发显著。经典蠕变模型中，幂律模型应用最广，通过应力指数（n）和激活能（Q）可粗略区分扩散蠕变（n=1）、位错攀移（n=5~7）、溶质拖拽（n=3）等主导机制。纯难熔金属蠕变多遵循幂律关系，W、Mo、Ta的 n值多在3~7之间，激活能与晶格扩散或位错核心扩散相关。细晶Nb则随应力呈现幂律蠕变与空位生成主导的双机制。合金体系中，W-Re-HfC和Mo-La2O3等通过析出相强化提升蠕变抗力，Ta基合金ASTAR-811C的蠕变性能依赖晶粒尺寸，Nb基合金C103受溶质拖拽机制控制。难熔高/中熵合金中，HfNbTaTiZr系以溶质拖拽为主要机制，同样的，WMoTaNb系中W含量升高可通过溶质拖拽效应增强抗蠕变能力。综合来讲，影响蠕变性能的因素包括成分和结构等本征因素，以及应力、工艺和服役环境等外在条件。本文为难熔金属在高温极端场景的应用提供了理论支撑，为高性能材料设计提供了指导。

Abstract:

This paper systematically reviews the creep properties and core mechanisms of refractory metals (W, Mo, Ta, Nb), their alloys, and refractory high/medium-entropy alloys. Creep, as a slow plastic deformation under constant stress at high temperatures, is regulated by the homologous temperature (TH). When TH < 0.3, it is dominated by dislocation glide; when 0.3 < TH < 0.5, it is controlled by the competition between strain hardening and recovery; when TH > 0.5, it exhibits three-stage creep, with the role of diffusion becoming increasingly prominent as temperature rises. Among classical creep models, the power-law model is the most widely used. Through the stress exponent (n) and activation energy (Q), it can roughly distinguish dominant mechanisms such as diffusion creep (n=1), dislocation climb (n=5~7), and solute drag creep (n=3). The creep of pure refractory metals mostly follows the power-law relationship. The n values of W, Mo, and Ta are mostly between 3 and 7, and their activation energies are related to lattice diffusion or dislocation core diffusion. In contrast, fine-grained Nb exhibits a dual mechanism dominated by power-law creep and vacancy generation depending on stress. In alloy systems, W-Re-HfC, Mo-La?O?, and others improve creep resistance through precipitation strengthening; the creep performance of the Ta-based alloy ASTAR-811C depends on grain size; and the Nb-based alloy C103 is controlled by the solute drag mechanism. Among refractory high/medium-entropy alloys, the HfNbTaTiZr system is mainly governed by the solute drag mechanism. Similarly, in the WMoTaNb system, the increase in W content can enhance creep resistance through the solute drag effect. Overall, the factors affecting creep performance include intrinsic factors such as composition and structure, as well as extrinsic conditions such as stress, processing technology, and service environment. This paper provides theoretical support for the application of refractory metals in high-temperature extreme scenarios and offers guidance for the design of high-performance materials.