The mechanical properties of novel hexagonal close-packed medium entropy alloy TiZrHf have been studied using first-principles method based on special quasi-random structure. The elastic properties and stress-strain relations of unitary Ti, Zr, Hf, binary alloys TiZr, TiHf and ZrHf have also been studied to benchmark the calculation accuracy. The derived elastic constants suggest the mechanical stability of TiZrHf alloy and all three binary alloys. The elastic constants of TiZrHf indicate a weak strengthening effect. Relatively, TiZrHf has larger strength and stiffness, and also exhibits small elastic anisotropy from several criteria. Especially, ideal strength is further studied. The ideal tensile strength (ITS) of TiZrHf along with all unitary and binary materials takes place in the [11$\overline{2}$0] direction. The ITS of TiZrHf is 3.87 GPa and the corresponding critical tensile strain is 0.08. The ideal shear strength (ISS) for all studied materials occurs in the (10$\overline{1}$0) <11$\overline{2}$0> shear system. The obtained ISS τ_{{10-10}[11-20]} for TiZrHf is 2.11 GPa at critical strain of ~0.09. The initial slopes of tensile and shear stress - strain curves correspond well to the tensile Young's modulus and shear modulus computed from elastic constants. Moreover, the resolved shear stress estimated from the ITS is smaller than the ISS τ_{{10-10}[11-20]} for each calculated alloy, indicating that the studied alloys are preference to shear slip before tensile failure. From shear stress-stain relation, the intrinsic shearability and half-width of the dislocation core are also studied for all calculated alloys. Then the inherent mechanism of mechanical properties of TiZrHf is further studied by examination of the detailed bond length distribution and the charge density distribution evolution. At critical point under tensile loading, the simultaneous breakdown of bonds results in a steep drop in tensile stress due to homogeneity. Whereas gradual breakdown of chemical bonds under shear deformation is predicted.

采用基于特殊准随机结构的第一性原理方法研究了新型六方密排中熵合金TiZrHf的力学性能。还研究了整体 Ti、Zr、Hf、二元合金 TiZr、TiHf 和 ZrHf 的弹性特性和应力应变关系，以衡量计算精度。导出的弹性常数表明 TiZrHf 合金和所有三种二元合金的机械稳定性。TiZrHf 的弹性常数表明强化效果较弱。相对而言，TiZrHf 具有更大的强度和刚度，并且从几个标准来看也表现出较小的弹性各向异性。特别是对理想强度进行了进一步研究。TiZrHf 以及所有单一和二元材料的理想拉伸强度 (ITS) 发生在 [11$\overline{2}$0] 方向。TiZrHf 的 ITS 为 3.87 GPa，相应的临界拉伸应变为 0.08。所有研究材料的理想剪切强度 (ISS) 出现在 (10$\overline{1}$0) <11$\overline{2}$0> 剪切系统。获得的TiZrHf ISS τ _{{10-10}[11-20]}在~0.09 的临界应变下为 2.11 GPa。拉伸和剪切应力-应变曲线的初始斜率与根据弹性常数计算的拉伸杨氏模量和剪切模量很好地对应。此外，从 ITS 估计的解析剪应力小于 ISS τ _{{10-10}[11-20]}对于每种计算出的合金，表明所研究的合金在拉伸破坏之前优先于剪切滑移。从剪切应力-染色关系，还研究了所有计算合金的固有剪切能力和位错核的半宽度。然后通过检查详细的键长分布和电荷密度分布演化，进一步研究了 TiZrHf 机械性能的内在机制。在拉伸载荷下的临界点，由于均匀性，键的同时断裂导致拉伸应力急剧下降。而预测在剪切变形下化学键会逐渐断裂。