DFT Study of Intrinsic Mechanical Properties of Mn2AlB2

Abstract

Mechanically strong materials are vital components of a high temperature tribosystem. We used density functional theory to investigate the intrinsic elastic and plastic properties of Mn2AlB2- a novel MAB phase tribomaterial. The most vulnerable slip system and direction of Mn2AlB2 are (100)[100] and [001], respectively. The ideal shear strength of Mn2AlB2 is 18.75 GPa and its ideal tensile strength is 20.56 GPa. The deformation mechanisms of Mn2AlB2 are closely related to its magnetic and bonding properties. The shear deformation mechanism involves the breaking of old bonds (i.e. Al-B), formation of new bonds (i.e. Mn-Al, Al-Al (along the a-axis)) and anisotropy of the existing bonds (i.e. Mn-B(short) and B-B). The lattice instability of Mn2AlB2 at the critical strains is triggered by abrupt changes in its magnetic behavior and subtle changes in its bonding properties. The predicted mode I, II and III fracture toughness of Mn2AlB2 are 1.88 MPa.m1/2, 1.58 MPa.m1/2 and 1.40 MPa.m1/2, respectively. This study elucidates the intrinsic mechanical behavior of Mn2AlB2 in terms of lattice stability and plasticity under different loading conditions for extreme environment applications.