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铸造锌铝合金稀土变质机理的电子理论研究

刘贵立 李荣德

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铸造锌铝合金稀土变质机理的电子理论研究

刘贵立, 李荣德

Electronic theoretical study on the modification mechanism of rare earth element s in zinc-aluminum cast alloys

Liu Gui-Li, Li Rong-De
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  • 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α 相与液相共存时的原子结构模型,利用递归方法计算了稀土固溶于晶粒内和富集于结晶前沿 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α相内溶解 度很小,结晶时富集于结晶前沿液体中的事实;稀土处于液态和晶态的结构能差相对于铝较 大解释了稀土在相界前的富集使α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,稀土处于结晶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理.
    The atomic structural model of the α phase-liquid interface region in ZA27 allo ys was set up by combining molecular dynamics theory with computer programming.T he electronic structure of α phase solid solution with rare earth elements and that of crystal-liquid growth front enriched with rare earth elements in the ZA2 7 casing 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.This explains the fact that the solid solubility of rare earth elem ents in α phase is very small,but large in the crystal-liquid growth front.The structural energy difference between the rare earth elements in the crystal-liqu id growth front and in the α phase is greater than that in Al,which support the view point that rare earth elements enriched in the crystal-liquid growth front can make α crystal-branch melt and break down,dissociate,and propagate.Calcula tions of bond order integrals (BOIs) also show that rare earth elements in the α phase-liquid growth front are not easier than Al to solidify on the surface o f α phase,so that the growth of α grains is blocked,and the alloy is refined,t hus illucidating the modification mechanism of rare earth elements from an elect ronic level for the zinc-aluminum cast alloys.
    • 基金项目: 教育部高等学校优秀教师资助计划(批准号:0027119)资助的课题.
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  • PDF下载量:  748
  • 被引次数: 0
出版历程
  • 收稿日期:  2002-11-19
  • 修回日期:  2002-12-22
  • 刊出日期:  2003-09-20

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