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

摘要

Through a combination of electronic structure,chemical bonding and mechanical property investigations,anisotropic electrical and mechanical properties,and damage tolerant ability of MAB phases Cr_5Si_3B and Hf_5Si_3B are predicted.The anisotropic electrical conductivity is due to the anisotropic distribution of Cr in Cr_5Si_3B and Hf in Hf_5Si_3B,which mainly contribute to the electrical conductivity.The anisotropic mechanical properties are underpinned by the anisotropic chemical bonding within the crystal structures of Cr_5Si_3B and Hf_5Si_3B.The high stiffness is determined by the strong covalent-ionic Cr1 B Cr1 and Cr1 Si bonds in Cr_5Si_3B and the ionic-covalent Hf1 B Hf1 and Si B bonds in Hf_5Si_3B;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,Cr_5Si_3B and Hf_5Si_3B are predicted tolerant to damage.The possible cleavage plane is(0001)and the possible slip systems are|{11 20}and|{0001}for both Cr_5Si_3B and Hf_5Si_3B.