Abstract
Compression experiments of the brittle MAX phase Ti2AlN were performed under confining gas pressure at room temperature. Subsequently, a complete dislocation analysis was performed by transmission electron microscopy. In particular, the Burgers vectors and the dislocation lines were studied via the weak beam technique: dislocation reactions are reported for the first time in a MAX phase, as well as dipole interactions. Footprints of a high lattice friction were also observed. All these features point towards classical dislocation activity, eventually leading to hardening.
Highlights
The ternary nitride Ti2AlN is a hexagonal layered compound belonging to the family of Mnþ1AXn phases, where n 1⁄4 1–3, M is a transition metal, A is an A-group element and X is nitrogen or carbon [1]
We present a transmission electron microscopy (TEM) analysis of Ti2AlN material synthetised by powder metallurgy and compressed under confining pressure at room temperature
TEM observations Figure 2 shows an area of interest with typical microstructure observed in deformed Ti2AlN; the diffraction condition is such that electrons are perpendicular to the basal plane and the used diffracting vector is g1 1⁄4 -1-120
Summary
The ternary nitride Ti2AlN is a hexagonal layered compound belonging to the family of Mnþ1AXn phases, where n 1⁄4 1–3, M is a transition metal, A is an A-group element and X is nitrogen or carbon [1]. The lattice anisotropy (c/a % 4.5) and the lamellar structure of Ti2AlN, as for all MAX phases, have a major impact on deformation mechanisms via the formation of kink and shear bands and eventually grain delaminations, leading to brittle-like behaviour below $800C [1,2]. Barsoum et al [3] suggested that only basal dislocations play a role in the plastic behaviour of MAX phases; due to the anisotropic and lamellar lattice, nucleation of dislocations is supposed to occur only in the basal plane. Recent experimental studies via atomic force microscopy (AFM) or TEM, have demonstrated that out-of-basal-plane dislocations exist in MAX phases, the nucleation and gliding of
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