First-Principles Study on Ni3Al (111) Antiphase Boundary with Ti and Hf Impurities (Postprint)
Journal Article - Open Access
AFRL Materials and Manufacturing Directorate Wright Patterson Air Force Base United States
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The effect of Ti and Hf impurities on the 111 antiphase boundary APB energy of Ni3Al is investigated via ab initio calculations. Cluster expansion is performed to predict supercell total energies sampled in a Monte Carlo approach that accounts for nondilute point defects at finite temperature, obtaining APB energies as a function of impurity concentration and temperature. Of the two ternary elements, Hf is more effective in increasing the APB energy. While the 111 APB energy of a pure L12 material requires at least second-nearest-neighbor interactions, we observe a strong correlation between impurity-induced APB energy enhancement and formation of rst-nearest-neighbor Ni-Ni bonds across the APB due to symmetry breaking. Using a linear-chain model and effective bond energies derived from effective cluster interactions, we propose a mechanism that explains why Hf is more effective than Ti.
- Properties of Metals and Alloys