NiCrAlFe精密电阻合金中的L12有序结构研究

First-Principles Study of Ordered Structures in NiCrAlFe Precision Resistance Alloy

摘要:

有序结构的形成是决定NiCrAlFe精密电阻合金电学性能的关键因素。本文利用第一性原理赝势平面波方法，计算了合金处于无序固溶体结构和形成L12型有序结构时的结合能、态密度、晶格常数等参数，并利用高分辨透射电子显微镜（HRTEM）对合金进行了结构表征，还测试了固溶态和时效态的电阻率。从结合能来看，该合金形成L12有序结构时比无序固溶体更加稳定；态密度以及部分态密度计算结果则表明，在L12有序结构中，Ni、Cr、Al、Fe会强烈成键而使得整个合金体系变得稳定；HRTEM分析结果证明固溶态合金经过和时效处理后出现了L12有序结构，而且该有序结构的晶格常数与计算值基本一致。对比无序固溶体与L12型有序结构费米能级处的态密度值发现，当形成L12有序结构时合金的导电能力较无序固溶体下降，电阻率升高，与实际测试结果吻合。

Abstract:

The forming of ordering structure in NiCrAlFe precision alloy is a vital factor for the electrical properties. Using the first-principles pseudopotential plane-wave method, the lattice constants, binding energies and density of states of an NiCrAlFe precision resistance alloy were calculated based on the disordering solid solution and L12-type ordering structures. The microstructure of the alloy was analyzed by high-resolution transmission electron microscope (HRTEM), also, the electrical resistance of the alloy was measured after solid-solution and aging treatment. From the binding energy point of view, the ordered structure is more stable than the disordered solid solution. The calculation results of density of states show that in the ordered structure, Ni, Cr, Al and Fe atoms bond with each other more strongly than they do in the disordered solid solution, and thus the stability of the alloy is improved. In fact, ordering structure with L12-type was revealed by HRTEM in the as-aged alloy, and its lattice parameter is close to the calculated result. According to the comparison of density of states at the Fermi level of different structures, the electrical conductivity of the alloy will decrease due to the formation of L12 ordered structure from the disordered solid solution, which is consistent with the experimental results.