關(guān)鍵界面的強化機理
(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083；
2. Materials Department, University of California, Santa Barbara, CA, 93106, USA)
摘 要: 本文總結(jié)回顧作者近年來從第一性原理出發(fā)，以應(yīng)用廣泛的高溫熱障涂層中γ-Ni(Al)/α-Al2O3關(guān)鍵界面為基礎(chǔ)，通過建立合理的熱力學(xué)模型，結(jié)合電子密度泛函計算，針對界面結(jié)合強度與溫度、原子化學(xué)配比和活度等的相關(guān)性所開展的一系列理論研究實踐。結(jié)果表明：在感興趣的溫度區(qū)間內(nèi)(1 300~1 600 K)，界面平衡相為富Al相，但靠近理想化學(xué)配比相的相界；富Al相界面的結(jié)合強度較高，約3倍于理想化學(xué)配比相界面的結(jié)合強度。雜質(zhì)S可向界面強烈富集，并嚴重削弱界面強度的60%~70%；活性元素Hf具有在基體中有效釘扎S、直接參與界面成鍵和在界面處置換S的3種界面強化效應(yīng)。
關(guān)鍵字: 熱障涂層界面；界面結(jié)合強度；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
