难熔高熵合金在高温下具有稳定性和优异的力学性能，被广泛应用于航空发动机、高速列车、燃气轮机等领域的高温结构中。这些领域要求材料在高温、高 压以及高应变率下保持优异的力学性能和结构稳定性。研究表明，难熔高熵合金 的室温拉伸塑性较差，严重制约了其工程应用。通过在基体中添加间隙氧原子能 够极大地改善难熔高熵合金的准静态拉伸塑性，实现良好的强度-塑性匹配。然 而，含氧难熔高熵合金在高应变率下的力学性能与变形机理尚不明确。鉴于此，本文利用实验和理论相结合，研究了 TiZrHfNb 和(TiZrHfNb)₉₈O₂难熔高熵合金在高温、高应变速率下的动态剪切韧性、应变率效应、温度效应，建立了难熔高熵合金高应变率下的力学响应与微结构关系，主要结论如下：

第一，TiZrHfNb 中添加 2%的氧原子后，基体中会形成有序氧复合体结构。 在塑性变形时，有序结构会改变局部应力场，从而激活位错交滑移，促进位错增 殖。在动态剪切变形后期，材料往往会形成绝热剪切带而导致失效。 (TiZrHfNb)₉₈O₂ 合金绝热剪切带周围塑性变形区较 TiZrHfNb 合金更大，滑移带 密度更高，表明在高应变率下有序氧复合体结构同样能够促进位错交滑移，提高 材料塑性变形能力。

第二，在773 K环境温度下，应变率为1x10³ s-1~4x10³ s^-1范围内，TiZrHfNb 合金的压缩强度约0.7 GPa，(TiZrHfNb)₉₈O₂合金的压缩强度约1.0 GPa，均未表 现出明显的率敏感性。氧原子的添加显著提高了TiZrHfNb难熔高熵合金在高温 高应变率下的压缩强度。理论分析表明，采用传统的 Johnson-Cook 模型对 TiZrHfNb 合金的强度进行预测，理论值与实验值相差较大。采用幂函数对J-C模 型中应变率系数和温度系数进行修正后，理论与实验值误差小于2%。

Refractory high-entropy alloys (RHEAs) have been widely applied in high-temperature structures, such as aerospace engines, high-speed trains, and gas turbines, due to their stability at high temperatures and excellent mechanical properties. These areas require materials to maintain excellent mechanical properties and structural stability under high temperatures, high pressures, and high strain rates. However, RHEAs exhibit poor tensile plasticity at room temperature, which severely restricts their applications. The addition of interstitial oxygen atoms to the matrix can significantly improve the quasi-static tensile plasticity of RHEAs, achieving a significant synergy of strength and ductility. However, the mechanical properties and deformation mechanisms of oxygen-containing RHEAs under high strain rates remain unclear. To this end, this paper combines experimental and theoretical methods to investigate the dynamic shear toughness, strain rate effect, and temperature effect of TiZrHfNb and (TiZrHfNb)98O2 RHEAs at high temperatures and high strain rates. The relationship between the mechanical response and microstructure of refractory HEAs under high strain rates have been established. The main conclusions are as follows:

First, the addition of 2% oxygen atoms into the matrix of TiZrHfNb results in the formation of ordered oxygen-rich compound structures(OOCs). During plastic deformation, the OOCS modifies the local stress field, thereby activating dislocation cross-slip and facilitating dislocation multiplication. In the later stages of dynamic shear deformation, materials often form adiabatic shear bands, leading to failure. In (TiZrHfNb)₉₈O₂ alloys, the plastic deformation region surrounding the adiabatic shear bands is larger compared to TiZrHfNb alloys, and the density of slip bands is higher. These results suggests that under high strain rates, the OOCs can also promote dislocation cross-slip and enhance the plastic deformation capability of the material.

Secondly, at 773 K and within a strain rate range of 1x10³ s-1~4x10³ s^-1 , the compressive strength of TiZrHfNb alloy is approximately 0.7 GPa, and that of (TiZrHfNb)₉₈O₂ alloy is approximately 1.0 GPa. Both RHEAs exhibit no significant strain rate sensitivity. The addition of oxygen atoms significantly enhances the compressive strength of TiZrHfNb refractory high-entropy alloy under high-temperature and high-strain-rate conditions. Theoretical analysis indicates that using the traditional J-C model to predict the strength of TiZrHfNb alloy results in a large deviation between theoretical and experimental values. By adjusting the strain rate and temperature coefficients in the J-C model using a power function, the discrepancy between theoretical and experimental values is reduced to less than 2%.