(沈陽工業(yè)大學(xué)材料科學(xué)與工程學(xué)院，沈陽110870)
摘 要: 通過基于密度泛函理論的第一原理計(jì)算方法，對Mg-Al-Y合金中的主要強(qiáng)化相，即Al2Y和Al3Y的相穩(wěn)定性、電子結(jié)構(gòu)、彈性性質(zhì)以及熱力學(xué)性質(zhì)進(jìn)行計(jì)算。相生成熱的計(jì)算結(jié)果表明：Al2Y和Al3Y均可穩(wěn)定存在，Al2Y的結(jié)構(gòu)穩(wěn)定性更強(qiáng)，因此，在合金的凝固過程中，Al2Y優(yōu)先析出。Al2Y和Al3Y的電子態(tài)密度(DOS)和差分電荷密度計(jì)算的結(jié)果表明：Al2Y和Al3Y兩相可以穩(wěn)定存在的內(nèi)在本質(zhì)在于Al原子與Y原子的價(jià)電子軌道發(fā)生強(qiáng)烈的相互作用，形成了spd雜化。兩相內(nèi)的原子成鍵均為共價(jià)鍵、離子鍵和金屬鍵。體模量B、剪切模量G、彈性模量E、泊松比ν和各向異性因子A等力學(xué)性質(zhì)參數(shù)的計(jì)算結(jié)果表明：這兩種相為強(qiáng)硬的脆性相并都為各向同性，因此，具有相似的強(qiáng)化效果。兩相熔點(diǎn)較高表明其具有很好的熱穩(wěn)定性，能夠提高合金的高溫性能。聲子譜和聲子態(tài)密度計(jì)算以及德拜溫度的計(jì)算結(jié)果進(jìn)一步驗(yàn)證了兩相具有結(jié)構(gòu)穩(wěn)定性較高。兩相的熱力學(xué)性質(zhì)符合一般熱力學(xué)規(guī)律，其中自由能的計(jì)算結(jié)果表明：兩相的穩(wěn)定性順序沒有發(fā)生變化。隨著溫度的升高，Al2Y的結(jié)構(gòu)穩(wěn)定性仍強(qiáng)于Al3Y的。
關(guān)鍵字: Mg-Al-Y合金；第一原理計(jì)算；相穩(wěn)定性；電子結(jié)構(gòu)；彈性；熱力學(xué)性質(zhì)
（School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110870, China）
Abstract:Phase stability, electronic structure, elastic and thermodynamic properties of Al2Y and Al3Y phases were investigated by means of first–principles calculations based on density functional theory (DFT). The results of formation enthalpy show that both two phases can stay stably, and Al2Y is more stable than Al3Y. Therefore, Al2Y has the priority to precipitate in the process of alloy solidification. The calculated density of state (DOS) and the electron density difference indicate that the phase stability of Al2Y and Al3Y is due to the strong interaction between valence electron orbits of Al and Y atoms, forming the spd hybridization. The bonding characteristics of Al2Y and Al3Y phases are all covalent bond, ionic bond and metallic bond. The calculated results of bulk modulus (B), shear modulus (G), elastic modulus (E), Poisson’s ratio ( ) and anisotropic coefficient (A) show that Al2Y and Al3Y phases are strong, hard and isotropic. Their similar mechanical properties contribute to their similar performance in Mg-Al-Y alloy. The phonon spectrum, phonon density of states and Debye temperature show their good structural stability as before. High melting points of Al2Y and Al3Y show that their strong thermal stability can improve the mechanical properties of alloy at high temperature. The thermodynamic properties of the two phases conform to the general laws, and the calculated free energy shows that the stability sequence of the two phases has not changed. With the increase of temperature, the structure stability of Al2Y is still better than that of Al3Y.
Key words: Mg-Al-Y alloy; first principles calculation; phase stability; electronic structure; elastic property; thermodynamic property
