Ag-Cu共晶合金非晶转变及晶化的分子动力学模拟
A Molecular Dynamics Study on Amorphous Formation and Crystallization of Ag-Cu Eutectic Alloys

作者: 黄 维 , 梁工英 :西安交通大学理学院材料物理系,西安;

关键词: 分子动力学模拟晶化转变组织形貌公共近邻分析(CNA) Molecular Dynamics Simulation Crystallization Morphology Common Neighbor Analysis (CNA)

摘要:

本文采用分子动力学方法研究了Ag-Cu共晶合金的结晶过程。依靠体系内能变化、公共近邻分析和原子可视化技术对Ag-Cu共晶合金的结构演变进行了分析。模拟结果表明,在10%~40%Cu范围内,随着Cu含量的增加,合金形成非晶结构的临界冷却速度减小,玻璃化转变温度增加。公共近邻分析的结果表明,在非晶晶化前的阶段,表征非晶结构的1551、1541和1431键对占据主要部分,但也存在少量的bcc和fcc晶核团簇。其中,表征正二十面体团簇的1551键对,随着Cu含量的增加而增加,表征缺陷二十面体团簇的1541和1431键对则相应减少,这表明,随着Cu含量的增加非晶体系的稳定性增加。与此同时,表征晶体相结构的键对随Cu含量的增加都有所减少,其中,bcc晶核的数量减少较小,但fcc晶核的数量却有较大的下降,从而使非晶晶化的形核核心减少,这也从结构上解释了非晶合金的玻璃化转变温度随成分增加而增加的现象。在非晶晶化以后,虽然体系以fcc结构为主,但仍存在一些无序的非晶态结构,这些结构存在于共晶两相界面,随Cu含量的增加而增加。利用可视化技术,我们可以发现,随着Cu含量的增加,Ag-Cu合金的共晶组织存在从固溶体形、网状共晶到层状共晶的演变。

Abstract: The crystallization of Ag-Cu alloys was studied by molecular dynamics method (MD) with embedded atom potential (EAM). The structural developments of Ag-Cu alloys were analyzed based on the variations of internal energy, common neighbor analysis (CNA), and atomic visualization technique. The simulation results showed that with the increase in Cu composition, the critical cooling rate of amorphous formation decreased and the glass-transition temperature of amorphous increased under the same heating rate. The results of CNA showed that the amorphous structure is main, and a few crystal clusters (bcc and fcc) are in it. Among the amorphous bond pairs, the pairs 1551 increases with the increase in Cu composition, which is the character of regular icosahedrons cluster. Meanwhile, the pairs 1541 and 1431, which are the character of defect icosahedrons clusters, reduce correspondingly. These show that the stability of amorphous increases. With the increase in Cu composition, the pairs 1441, 1661 and 1421 are all reduced, the 1441 and 1661 decrease little and the 1421 decreases great, which implies that the nuclei reduce during the crystallization of amorphous and the glass-transition temperature increases. After crystallization, the fcc structure is dominant but there are a few defect icosahedrons clusters between the eutectic boundaries. Moreover, the eutectic structure of Ag-Cu alloys can be transformed from solid solution, net-like into the lamellar morphologies with composition during the solidification and crystallization.

文章引用: 黄 维 , 梁工英 (2013) Ag-Cu共晶合金非晶转变及晶化的分子动力学模拟。 应用物理, 3, 149-154. doi: 10.12677/APP.2013.38028

参考文献

[1] S. McDonald, K. Nogita, J. Read, et al. Influence of composition on the morphology of primary Cu6Sn5 in Sn-4Cu alloys. Journal of Electronic Materials, 2013, 42(2): 256-262.

[2] L. R. Garcia, W. R. Osorio and A. Garcia. The effect of cooling rate on the dendritic spacing and morphology of Ag3Sn intermetallic particles of a SnAg solder alloy. Materials & Design, 2011, 32(5): 3008-3012.

[3] P. R. tenWolde, M. J. RuizMontero and D. Frenkel. Numerical calculation of the rate of crystal nucleation in a Lennard-Jones system at moderate undercooling. The Journal of Chemical Physics, 1996, 104(24): 9932-9947.

[4] N. Iqbal, N. H. Van Dijk, S. E. Offerman, et al. Real-time observation of grain nucleation and growth during solidification of aluminium alloys. Acta Materialia, 2005, 53(10): 2875-2880.

[5] L. Qi, L. F. Dong, S. L. Zhang, et al. Glass formation and local structure evolution in rapidly cooled Pd55Ni45 alloy melt: Molecular dynamics simulation. Computational Materials Science, 2008, 42(4): 713-716.

[6] J. Liu, J. Z. Zhao, Z. Q. Hu. MD study of the glass transition in binary liquid metals: Ni6Cu4 and Ag6Cu4. Intermetallics. 2007, 15(10): 1361-1366.

[7] S. H. Kim, T. H. Kim, J. W. Bae, et al. Thermal stability of AgxCu1-x alloys and Pt capping layers for GaN vertical light emitting diodes. Thin Solid Films, 2012, 521: 54-59.

[8] K. Shin, D. H. Kim, S. C. Yeo, et al. Structural stability of AgCu bimetallic nanoparticles and their application as a catalyst: A DFT study. Catalysis Today, 2012, 185(1): 94-98.

[9] J. J. Morrier, G. Suchett-Kaye, D. Nguyen, et al. Antimicrobial activity of amalgams, alloys and their elements and phases. Dental Materials, 1998, 14(2): 150-157.

[10] S. Takayama. Amorphous structures and their formation and stability. Journal of Materials Science. 1976, 11(1): 164-185.

[11] W. G. Hoover. Canonical dynamics: Equilibrium phase-space distributions. Physical Review A, 1985, 31(3): 1695-1697.

[12] W. G. Hoover. Constant-pressure equations of motion. Physical Review A, 1986, 34(3): 2499-2500.

[13] L. Verlet. Computer “Experiments” on Classical Fluids. I. Ther- modynamical Properties of Lennard-Jones Molecules. Physical Review, 1967, 159(1): 98-103.

[14] M. S. Daw, M. I. Baskes. Semiempirical, Quantum Mechanical Calculation of Hydrogen Embrittlement in Metals. Physical Review Letters, 1983, 50(17): 1285-1288.

[15] M. S. Daw, M. I. Baskes. Embedded-atom method: Derivation and application to impurities, surfaces, and other defects in metals. Physical Review B, 1984, 29(12): 6443-6453.

[16] X. W. Zhou, H. N. G. Wadley, R. A. Johnson, et al. Atomic scale structure of sputtered metal multilayers. Acta Mater, 2001, 49(19): 4005-4015.

[17] J. D. Honeycutt, H. C. Andersen. Molecular dynamics study of melting and freezing of small Lennard-Jones clusters. The journal of physical chemistry, 1987, 91(19): 4950-4963.

[18] H. Tsuzuki, P. S. Branicio, J. P. Rino. Structural characterization of deformed crystals by analysis of common atomic neighborhood. Computer Physics Communications, 2007, 177(6): 518- 523.

分享
Top