铸造锌铝合金稀土变质机制的电子理论研究  

Electronic Theoretical Study on Modification Mechanism of Rare Earth Elements in Zinc-Aluminum Casting Alloys

作　　者：刘贵立[1] 李荣德[1] 

机构地区：[1]沈阳工业大学材料科学与工程学院,辽宁沈阳110023

出　　处：《中国稀土学报》2003年第5期554-557,共4页Journal of the Chinese Society of Rare Earths

基　　金：教育部高等学校优秀教师资助计划资金资助(0027119)项目

摘　　要：根据分子动力学理论建立了液态锌铝合金ZA27的模型,结合计算机编程构造出了ZA27合金相与液相共存时的原子结构模型,利用Recursion方法计算了稀土固溶于晶粒内和富集于晶界前沿时的电子结构。由此得出:稀土处于相界区比在晶内更稳定,从而解释了稀土在相内溶解度很小,结晶时富集于相界前沿液体中的事实;稀土处于液态和晶态的结构能差相对于铝较大,解释了稀土在晶界前的富集使晶枝产生熔断、游离、增殖的观点。原子间的键级积分计算也表明,稀土处于晶界前沿液体中与铝相比不容易结晶到晶体表面,起到阻碍晶粒长大,细化晶粒的作用,这就从电子层次解释了稀土的变质机制。The atom structure model of the phase-liquid interface region in ZA27 alloys was set up by molecular dynamics theory and computer programming. Electronic structures of α phase with rare earth elements and that of crystal-liquid growth front with rare earth element enrichment in ZA27 casting alloy were investigated by the Recursion method. The calculated results show that rare earth elements are more stable in the phase interface region than in α phase, which explains the poor solid solubility of rare earth elements in α phase, and the enrichment of rare earth elements in the crystal-liquid growth front. The structure energy difference of rare earth element in the crystal-liquid growth front relative to α phase is bigger than that of Al, which explains the enrichment of rare earth elements in the crystal-liquid growth front and the mechanism of crystal-branch melt, breakdown, dissociation and propagation. Calculations of bond order integrals (BOIs) also show that rare earth elements compared with Al in the α phase-liquid growth front are not easier to solidify on the surface of α phase. Therefore the growth of α grain is blocked and the alloy is refined, which interprets the modification mechanism of rare earth elements from electronic level in zinc-aluminum casting alloys.

关 键 词：金属材料 相与液相相界原子结构模型 Recursion方法 电子结构 稀土变质机制 稀土 

分 类 号：TG111.1[金属学及工艺—物理冶金]