Interface Bonding Nature and Tensile Behaviour of Ti2alc(0001)/Tic(111) Interface from First-Principles Calculation

Abstract

Using first principles, a systematic investigation of interface bonding nature and tensile behaviour of Ti2AlC(0001)/TiC(111) interface has been carried at the atomic scale. The results show that Ti(Al)-on-top-C2 has the largest work of adhesion (13.1160 J/m2), the smallest interface energy (-2.6161 J/m2), and the largest interface fracture toughness (3.9660-4.9372 MPa·m1/2). Its interfacial bond is Ti-C covalent bond. And its tensile properties (critical strain of 12% and ideal tensile strength of 26.32 GPa) are second only to the best tensile properties (13% and 28.73 GPa). In the tensile simulation, fracture locations of seven interface models are the same as those of Griffith theory and work of interface separation, except for Ti(Al)-fcc-hollow-Ti3. Inconsistency is due to mutual repulsion of two Ti atoms of Ti2-Ti3 bond in Ti(Al)-fcc-hollow-Ti3. And movement of C atoms on Ti2AlC bulk of C1-C2 bond changes stacking site from “hcp-hollow” to “on-top”, which leads to a decrease in stress of C-hcp-hollow-C2 before inflection point. Fracture process of the interface is summarized as follows: firstly smaller electron holes are formed at lower strains, then electron microcrack is formed as strain increases, and ultimately fracture failure occurs due to break of chemical bond allowing charge depletion region to form.

Keywords: Ti2AlC/TiC interface, First-principles calculation, Interface fracture toughness, Tensile properties, Fracture process