(1. 長(zhǎng)沙理工大學(xué) 工程車輛輕量化與可靠性技術(shù)湖南省高校重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙410114；
2. 長(zhǎng)沙理工大學(xué) 工程車輛安全性設(shè)計(jì)與可靠性技術(shù)湖南省重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410114；
3. 湖南大學(xué) 材料與科學(xué)工程學(xué)院，長(zhǎng)沙 410082)
摘 要: 采用基于密度泛函理論的第一性原理計(jì)算方法，從理論上系統(tǒng)研究不同Al固溶濃度x(x=0~1)下面心立方(FCC)結(jié)構(gòu)Cr1-xAlxN硬質(zhì)刀具涂層的微觀幾何構(gòu)型、相結(jié)構(gòu)穩(wěn)定性及其熱分解機(jī)制，并從電子結(jié)構(gòu)角度對(duì)其穩(wěn)定性起源進(jìn)行分析。結(jié)果表明：隨著Al固溶濃度增大，F(xiàn)CC-Cr1-xAlxN晶胞逐漸收縮，而其晶格畸變程度卻先增大后減小，且當(dāng)Al濃度x為0.5~0.75時(shí)，F(xiàn)CC-Cr1-xAlxN晶格畸變較為嚴(yán)重，為析出密排六方(HCP)結(jié)構(gòu)的AlN化合物提供源動(dòng)力；隨著Al固溶濃度增大，F(xiàn)CC-Cr1-xAlxN相結(jié)構(gòu)穩(wěn)定性逐漸降低，且其極易按FCC-Cr1-xAlxN→(FCC-CrN)+(HCP-AlN)→(HCP-Cr2N)+N2+(HCP-AlN)的路徑進(jìn)行分解，計(jì)算結(jié)果與實(shí)驗(yàn)保持一致；Al固溶致使FCC-Cr1-xAlxN相結(jié)構(gòu)穩(wěn)定性降低的內(nèi)在原因在于Cr1-xAlxN晶胞中Cr—N共價(jià)鍵作用隨Al固溶度的增大而逐漸減弱。
關(guān)鍵字: CrAlN；硬質(zhì)刀具涂層；相結(jié)構(gòu)穩(wěn)定性；熱分解機(jī)制；第一性原理計(jì)算
（1. Key Laboratory of Lightweight and Reliability Technology for Engineering Vehicle,
Education Department of Hunan Province, Changsha University of Science and Technology, Changsha 410114, China;
2. Key Laboratory of Security Design and Reliability Technology for Engineering Vehicle,
Education Department of Hunan Province, Changsha University of Science and Technology, Changsha 410114, China;
3. College of Materials Science and Engineering, Hunan University, Changsha 410082, China）
Abstract:Using first-principles calculations method based on density functional theory, the microscopic geometric configurations, phase structure stability and thermal decomposition mechanism of the face-centered cubic (FCC) Cr1-xAlxN (x=0~1) hard cutting tool coating with different aluminum solution concentrations were systematically studied. The origin of phase structure stabilities were also analyzed from the perspective of electronic structures. The results show that the crystal cell of FCC-Cr1-xAlxN gradually contracts with the increase of Al solid solubility, while the magnitude of lattice distortion becomes large firstly, and then becomes small. The magnitude of lattice distortion is the largest when the Al concentration x is 0.5-0.75, which provids the driving force for the precipitation of hexagonal close-packed (HCP) AlN compound. The calculations of cohesive energy and decomposition enthalpy reveal that the phase structure stability of FCC-Cr1-xAlxN is gradually weakened with the increase of Al solid solubility, and it is likely to decompose according to the paths of FCC-Cr1-xAlxN→(FCC-CrN)+(HCP-AlN)→(HCP-Cr2N)+N2+(HCP-AlN). The analysis of electronic structures indicates that the intrinsic reason of the weakened phase structure stability of FCC-Cr1-xAlxN with Al solid solution should be attributed to the weakened covalent bond strength between Cr and N in Cr1-xAlxN crystal cell with the increase of Al solid solubility.
Key words: CrAlN; hard cutting tool coating; phase structure stability; thermal decomposition mechanism; first-principles calculation
