Abstract
We present a modified embedded atom method (MEAM) semi-empirical force-field model for the Ti1−xAlxN (0 ≤ x ≤ 1) alloy system. The MEAM parameters, determined via an adaptive simulated-annealing (ASA) minimization scheme, optimize the model’s predictions with respect to 0 K equilibrium volumes, elastic constants, cohesive energies, enthalpies of mixing, and point-defect formation energies, for a set of ≈40 elemental, binary, and ternary Ti-Al-N structures and configurations. Subsequently, the reliability of the model is thoroughly verified against known finite-temperature thermodynamic and kinetic properties of key binary Ti-N and Al-N phases, as well as properties of Ti1−xAlxN (0 < x < 1) alloys. The successful outcome of the validation underscores the transferability of our model, opening the way for large-scale molecular dynamics simulations of, e.g., phase evolution, interfacial processes, and mechanical response in Ti-Al-N-based alloys, superlattices, and nanostructures.
Highlights
Ti1−x Alx N (0 ≤ x ≤ 1) alloys are widely used for wear and oxidation protection of metal cutting and forming tools, aerospace components, and automotive parts [1,2]
modified embedded atom method (MEAM) results for lattice parameters are in excellent agreement with density functional theory (DFT) and experimental data
From a quantitative point of view, the cohesive energy difference Ec,B3-AlN – Ec,B4-AlN of 30 meV/atom calculated from MEAM is within the range of DFT
Summary
Ti1−x Alx N (0 ≤ x ≤ 1) alloys are widely used for wear and oxidation protection of metal cutting and forming tools, aerospace components, and automotive parts [1,2]. Far-from-equilibrium conditions, which prevail during vapor-based thin-film deposition [4], enable synthesis of metastable B1-Ti1−x Alx N solid solutions for x ≤ 0.7 [5] These metastable alloys undergo, in the temperature range ≈1000 to ≈1200 K, spinodal decomposition into strained isostructural Al-rich and Ti-rich B1-Ti1−x Alx N domains, which in turn, results in an age-hardened material with superior high-temperature mechanical and oxidation performance [6]. Despite the knowledge generated from these investigations, atomic-scale processes that drive phase transformations (including spinodal decomposition) and elastic/plastic response in B1-Ti1−x Alx N alloys (0 ≤ x ≤ 1) are poorly understood. This is because the time and length scales at which these processes occur often lie beyond the temporal and spatial resolution
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