Cr–Al–B ternary borides are considered as promising materials to apply in high temperature environment due to their outstanding thermal properties. However, the detail mechanical properties of these borides are still not very clear. To better exploit the potential ability of these borides, some basic physical-chemical properties such as structure stability, stiffness, hardness especially for anisotropic elasticity and sound velocity are studied by first-principles calculations. The results showed that there are four compounds, namely CrAlB, Cr₂AlB₂, Cr₃AlB₄ and Cr₄AlB₆, have a stable crystal structure. The Cr₄AlB₆ is the most in-compressible and stiff boride and the Cr₂AlB₂ is the most brittle boride among the Cr–Al–B TMBs. In addition, the strongest shear anisotropic degree of the CrAlB is along (100) crystal plane while the Cr₃AlB₄, Cr₄AlB₆ and Cr₂AlB₂ are along (010) crystal plane. The bulk moduli profile of the Cr–Al–B TMBs are almost spherical, especially observed in projection of (001), (010) and (100) planes which indicate that the bulk modulus is weak anisotropy. The Cr₄AlB₆ has a larger Debye temperature than the other borides. This work will provide some helpful statistics for further investigating Cr–Al–B ternary borides with outstanding mechanical and thermal properties.

Cr-Al-B三元硼化物因其出色的热性能而被认为是在高温环境中应用的有希望的材料。但是，这些硼化物的详细机械性能仍然不是很清楚。为了更好地利用这些硼化物的潜在能力，通过第一性原理计算研究了一些基本的物理化学性质，例如结构稳定性，刚度，硬度，尤其是各向异性弹性和声速。结果表明，CrAlB，Cr ₂ AlB ₂，Cr ₃ AlB ₄和Cr ₄ AlB ₆四种化合物具有稳定的晶体结构。Cr ₄ AlB ₆是最不可压缩且最坚硬的硼化物，而Cr ₂ AlB ₂是Cr–Al–B TMB中最脆的硼化物。另外，CrAlB的最强剪切各向异性度沿着（100）晶面，而Cr ₃ AlB ₄，Cr ₄ AlB ₆和Cr ₂ AlB ₂沿着（010）晶面。Cr-Al-B TMBs的体积模量轮廓几乎是球形的，特别是在（001），（010）和（100）平面的投影中观察到，这表明体积模量是各向异性的。Cr ₄ AlB ₆具有比其他硼化物更大的德拜温度。这项工作将为进一步研究具有优异机械和热性能的Cr-Al-B三元硼化物提供一些有用的统计数据。