(TiVZrTaWx)100-yNy低活化难熔高熵合金强度、塑性协同优化

Synergistic Optimization of Strength and Plasticity for Low-Activation (TiVZrTaWx)100‒yNy Refractory High-Entropy Alloys

摘要:

难熔高熵合金大多表现出较高的强度，但是其室温塑性有限。其强度的提升通常依赖于晶格畸变、固溶强化等，这会限制位错运动进而降低塑性；而塑性提升所依赖的强化机制往往会削弱强度强化效果，因此合金强度、塑性的协同提升一般难以兼顾。为解决这一问题，本研究设计并制备了TiVZrTaW_x（x=5, 10, 15, 20）低活化难熔高熵合金，分析了W含量对合金相结构、微观组织以及压缩力学性能的影响，发现当W含量增加至10%时，合金实现了强度和塑性的协同提升，其硬度、屈服强度和塑性分别为535.7 HV、1808.85 MPa和7.22%。分析其原因，主要可归因于固溶强化和第二相强化。为进一步提升合金的综合力学性能，向TiVZrTaW₁₀合金中添加了不同含量的非金属元素N。结果表明(TiVZrTaW₁₀)_100–yN_y难熔高熵合金的强度和塑性同时得到进一步提升，其中(TiVZrTaW₁₀)_98.5N_1.5合金的硬度、屈服强度和塑性分别达到605.8 HV、2008.66 MPa和11.25%。通过TEM等分析发现，其力学性能的提升主要源于第二相强化、压缩变形中基体和第二相的协同变形以及N元素掺入引起的间隙强化。

Abstract:

Refractory high-entropy alloys (RHEAs) usually exhibit high strength but limited plasticity at room temperature. Their strength enhancement depends on the mechanisms such as lattice distortion and solid-solution strengthening, which restrict dislocation motions and thus reduce their plasticity. In contrast, the strengthening mechanisms that improve plasticity often weaken strengthening effect. Therefore, enhancing both strength and plasticity simultaneously remains a significant challenge for RHEAs. To address this issue, TiVZrTaW_x (x=5, 10, 15, 20) low-activation RHEAs were designed and prepared, and the effects of W content on the phase structure, microstructure, and compressive mechanical properties were investigated. The results show that increasing the W content to 10% can enhance both the strength and plasticity simultaneously, and the TiVZrTaW₁₀ RHEA shows a hardness of 535.7 HV, a yield strength of 1808.85 MPa and a plasticity of 7.22%. Such improvement is mainly attributed to the solid-solution strengthening and secondary-phase strengthening effects. To further enhance the mechanical properties, a minor amount of N was added to the TiVZrTaW₁₀ RHEA. The results show that the strength and plasticity of the (TiVZrTaW₁₀)_100?yN_y RHEAs are further improved. The typical (TiVZrTaW₁₀)_98.5N_1.5 RHEA exhibits a hardness of 605.8 HV, a yield strength of 2008.66 MPa, and a plasticity of 11.25%. Through TEM and other analyses, the enhanced mechanical properties are found to mainly result from the secondary-phase strengthening, synergistic deformation of the matrix and secondary phases during compression, and interstitial strengthening effects induced by N addition.