Elastic isotropy originating from heterogeneous interlayer elastic deformation in a Ti3SiC2 MAX phase with a nanolayered crystal structure

The elastic properties of a single-crystalline Ti3SiC2 MAX phase with a nanolayered crystal structure, comprising Ti-Si and two distinct Ti-C bonding layers, that had remained unclear because of the difficulty in growing large single crystals, were studied. Rather than unavailable large single crystals, polycrystalline samples with a crystallographic texture were prepared. By analyzing the polycrystalline elastic constants on the basis of an inverse Voigt-Reuss-Hill approximation, the elastic properties of a single crystal Ti3SiC2 with a hexagonal symmetry were determined. This revealed that the single-crystalline Young's modulus was almost isotropic despite its highly anisotropic layered structure. The shear modulus for (0001)< 11 (2) over bar0 > was higher than that for {11 (2) over bar0}[0001] in contrast to the basal slip-dominated plastic deformation reflecting the layered structure. Furthermore, first-principles calculations revealed that heterogeneous interlayer elastic deformation caused by the stabilization of Ti-Si bonding is the origin of the elastic isotropy in a Ti3SiC2 MAX phase.

Automated summary

In this study, the elastic properties of single-crystalline Ti3SiC2 MAX phase were investigated using polycrystalline samples with crystallographic texture. The results showed that despite its highly anisotropic layered structure, the single-crystalline Young's modulus was almost isotropic, with differences in shear modulus depending on crystallographic directions. First-principles calculations suggested that heterogeneous interlayer elastic deformation due to Ti-Si bonding stabilization is the origin of the elastic isotropy in Ti3SiC2 MAX phase.