Cr5Si3B and Hf5Si3B: New MAB phases with anisotropic electrical, mechanical properties and damage tolerance

Through a combination of electronic structure, chemical bonding and mechanical property investigations, anisotropic electrical and mechanical properties, and damage tolerant ability of MAB phases Cr5Si3B and Hf5Si3B are predicted. The anisotropic electrical conductivity is due to the anisotropic distribution of Cr in Cr 5Si3B and Hf in Hf5Si3B, which mainly contribute to the electrical conductivity. The anisotropic mechanical properties are underpinned by the anisotropic chemical bonding within the crystal structures of Cr5Si3B and Hf5Si3B. The high stiffness is determined by the strong covalent-ionic Cr1-B-Cr1 and Cr1-Si bonds in Cr5Si3B and the ionic-covalent Hf1-B-Hf1 and Si-B bonds in Hf5Si3B; while the low shear deformation resistance is attributed to the presence of metallic Cr-Cr, Hf-Hf and Si-Si bond. Based on the low Pugh's ratio, Cr5Si3B and Hf5Si3B are predicted tolerant to damage. The possible cleavage plane is (0001) and the possible slip systems are <1 (1)over-bar00>vertical bar{11 (2)over-bar0} and <11 (2)over-bar0>vertical bar{0001} for both Cr5Si3B and Hf5Si3B. (C) 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.