Mechanical Behavior and Deformation Mechanisms of CrB ₄ Subjected to Compressive-Shear Loadings

Chromium tetraboride (CrB4) has attracted widespread interest due to its high hardness, compressive strength, and wear resistance. Although its mechanical properties under simple loading conditions have been studied, its response and deformation mechanisms under complex stress states remain poorly understood. In this work, first-principles calculations were employed to investigate the mechanical response and microstructural evolution of CrB4 under tensile, pure shear, and coupled compressive-shear stress conditions. It was found that the [001] orientation in the (100) plane is the weakest shear direction under pure shear loading conditions. It was also found that the dependence of shear strength on normal stress is nonmonotonic: shear stress increases with σzz at low normal stress (σzz ≤ 40 GPa), consistent with classical strengthening mechanisms, but exhibits pronounced softening beyond this threshold. Finally, a generalized Mohr–Coulomb model incorporating strain and normal stress effects on the friction coefficient was developed to describe the dependence of shear stress and normal stress at different strains obtained by first-principles calculations. These findings can provide new insights into the complex deformation mechanisms of CrB4 under multiaxial loading, which will be helpful for its design and optimization under high-pressure conditions.