Ni-Fe坡莫合金中短程有序与长程有序的扩散率和动力学
Diffusivities and kinetics of short-range and long-range orderings in Ni-Fe permalloys
AI总结：
本文建立原子扩散微观模型并结合静态浓度波与自洽场方法，研究Ni-Fe坡莫合金短程及L12型长程有序弛豫，估算扩散率并揭示成分与温度的影响。
摘要：
本文考虑用原子扩散的微观模型来描述f.c.c.-Ni-Fe坡莫合金中的短程有序弛豫动力学。该模型同时考虑了相互作用原子在浓度非均匀性长程场中原子跳跃的离散性和各向异性特征。利用所评估的原子跳跃概率，估算了无序Ni-Fe坡莫合金的扩散系数和激活能。结果表明，在成分固定时温度升高对原子间相互作用的“势”场具有非单一影响：对于某些确定的配位壳层，该“势”场增强，而对于其他一些配位壳层则减弱。尽管温度升高通常会促进所有原子跳跃概率的增加，但由确定元素的原子产生、并由其浓度非均匀性引起的“势”场对远处格点作用的减弱，会导致该元素原子跳跃概率的增加，首先是增加到距离非均匀性“源”更远的格点。在静态浓度波方法与自洽场近似的框架内，得到了用于描述L12型超结构长程有序弛豫的Onsager型动力学方程。为计算有序Ni3Fe坡莫合金的扩散率，使用了关于长程有序参数弛豫的独立衍射实验数据。绘制了非化学计量比f.c.c.-Ni-Fe坡莫合金长程有序时间演化的理论曲线。合金元素浓度的降低会导致长程有序参数变化减慢，并使其弛豫时间增加。
英文摘要：
The microscopic model of atomic diffusion is considered to describe the short-range order relaxation kinetics within the f.c.c.-Ni-Fe Permalloys. The model takes into account both the discrete and anisotropic characters of atomic jumps within the long-range field of concentration heterogeneities of the interacting atoms. The diffusion coefficients and activation energies for the disordered Ni-Fe permalloy are estimated with the evaluated probabilities of atomic jumps. As shown, the increasing of a temperature with a fixed composition influences on the 'potential' field of interatomic interaction ambiguously: the field 'potential' increases for defined coordination shells and decreases for some of other ones. Although the temperature increasing promotes the increasing of any atomic-probabilities jumps generally, but decreasing of the action of 'potential' field generated by the atoms of defined element and caused by its concentration heterogeneities onto the distant sites results in increasing of the atomic-jumps' probabilities of just this element, first of all, into the sites, which are more distant from the 'source' of heterogeneity. Within the framework of the static concentration waves' method along with the self-consistent field approximation, the Onsager-type kinetics equation is obtained to describe the long-range order relaxation by the L12-type superstructure. To calculate diffusivities for the ordered Ni3Fe permalloy, the independent, diffraction experimental data of the long-range order parameter relaxation are used. Theoretical curves of the long-range order time evolution for the non-stoichiometric f.c.c.-Ni-Fe permalloys are plotted. Decreasing of the concentration of alloying element results in decelerating of the long-range order parameter change and in increasing of its relaxation time.
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