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 out 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). Except for Ti(Al)-fcc-hollow-Ti3, the fracture locations of seven interface models in the tensile simulation correspond to Griffith theory and work of interface separation. The inconsistency arises from the mutual repulsion of two Ti atoms in the 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. The fracture process of the interface is summarized as follows: tiny electron holes form at lower strains, followed by electron microcrack as strain increases, and finally fracture failure due to the breakage of the chemical bond allowing the charge depletion region to form.

Keywords

• Ti2AlC/TiC interface
• First-principles calculation
• Interface fracture toughness
• Tensile properties
• Fracture process