关键界面的强化机理
(1. 中南大学 材料科学与工程学院，长沙 410083；
2. Materials Department, University of California, Santa Barbara, CA, 93106, USA)
摘 要: 本文总结回顾作者近年来从第一性原理出发，以应用广泛的高温热障涂层中γ-Ni(Al)/α-Al2O3关键界面为基础，通过建立合理的热力学模型，结合电子密度泛函计算，针对界面结合强度与温度、原子化学配比和活度等的相关性所开展的一系列理论研究实践。结果表明：在感兴趣的温度区间内(1 300~1 600 K)，界面平衡相为富Al相，但靠近理想化学配比相的相界；富Al相界面的结合强度较高，约3倍于理想化学配比相界面的结合强度。杂质S可向界面强烈富集，并严重削弱界面强度的60%~70%；活性元素Hf具有在基体中有效钉扎S、直接参与界面成键和在界面处置换S的3种界面强化效应。
关键字: 热障涂层界面；界面结合强度；第一性原理；密度泛函；活性元素
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Materials Department, University of California, Santa Barbara, CA, 93106, USA）
Abstract:A systematic strategy was proposed and overviewed to predict the adhesion strength of metal/oxide interfaces, with the technologically-important γ-Ni(Al)/α-Al2O3 interface as an example. The atomistic density functional theory (DFT) calculations were carried out to assess the effects of temperature, interfacial stoichiometry, Al activity, S segregation and Hf doping on the adhesion. Computations of the Al activity in Ni(Al) and the interfacial phase diagram between 1 300 and 1 600 K suggest that the interface phase is Al-riched phase, but close to the boundary with the stoichiometric phase. The Al-riched phase has significantly stronger adhesion than the stoichiometric phase. While S can substantially decrease the adhesion by 60%−70%, alloying with reactive-element Hf substantially improves the adhesion through three strengthening mechanisms: pinning S in bulk Ni(Al), displacing S from its interstitial interfacial sites, and directly enhancing the interfacial bonds.
Key words: thermal barrier coating (TBC); interface adhesion; first-principles density functional theory; reactive element
