Point defect behavior and its relation to the material properties in B2-type Intermetallic compounds.

B2 型金属间化合物中点缺陷行为及其与材料性能的关系。

基本信息

批准号：
10650694
负责人：
KOGACHI Mineo
金额：
$ 2.24万
依托单位：
Osaka Prefecture University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Point defects which exist as a stable state in metals and alloys in any temperatures and compositions are well established to strongly affect their material properties. Aim of the present research is to determine the point defect structure in the intermetallic compounds with B2-type ordered structure by means of powder X-ray and neutron diffraction measurements and also to discuss the defect formation mechanism in these B2-type intermetallics by thermodynamic treatment.Point defects determined for B2 FeAl alloys showed a certain hybrid state in which four kinds of point defect generally appears, similarly as has already been reported for B2 NiAl and CoAl alloys by our research group. Further, two curious features were found in point defect behavior, that is with increasing in temperature, first, thermal vacancies are created on both Fe and Al sites (random vacancy distribution, RVD) and second, antisite atoms tend to recover into their own sites (antisite atom recovering, ASAR). These … More situations can never be interpreted within a framework of the defect model previously proposed.Thermodynamic treatment on the point defect formation in B2-type alloys was developed based on the Bragg-Williams method. In constructing the defect model, it was assumed : (1) constitutional defect in the ground state is the antisite atom and (2) defect behavior due to the temperature increase can be described as a hybrid state where the RVD reaction and the ASAR and other reactions succeeding the RVD process simultaneously occur. Numerical results for NiAl and FeAl alloys reproduced well their observed trends, e.g., the preferable formation of Ni (Fe) vacancies and a certain creation of the antisite Al atoms in both systems, and in the FeAl, the RVD and ASAR like behaviors.Vacancy concentration in B2 AuCd alloys was obtained as a function of composition. It showed a rapid increase above 49.5%Cd and reached to about 1% at 51.5%Cd, which is comparable with the results in B2 FeAl alloys. So, the point defect behavior can be expected to be a similar hybrid one as in the FeAl. B2 AuCd alloys transform to the martensite phase when decreasing in temperature. The 'martensite ageing effect' appearing in ageing in the martensitic state is believed to related to the point defect behavior. Changes in the lattice constant and the integrated intensities of fundamental and superlattice reflections due to martensite ageing were measured for slow-cooled and water-quenched Au-49.8Cd alloy. The results showed no detectable change, indicating that vacancy migration and also long-range ordering during ageing do not occur. This suggests an independence of the long-range order on the martensite ageing effect in this alloy. Less

在任何温度和组成中，在金属和合金中都存在的点缺陷均得到很好的确定，从而强烈影响其材料特性。本研究的目的是通过粉末X射线和中子衍射测量值确定具有B2型有序结构的金属间化合物中的点缺陷结构，还讨论了这些B2型金属层中的缺陷形成机制通过热力学治疗中的B2型缺陷。我们的研究小组的B2 NIAL和煤合金。此外，在点缺陷行为中发现了两个奇怪的特征，即温度的升高，首先是在Fe和Al地点（随机空位分布，RVD）和第二个抗岩原子往往会恢复到自己的位置（Antisite Atom Recessing，Asar，Asar）。这些……更多的情况永远无法在先前提出的缺陷模型的框架内解释。基于Bragg-Williams方法，开发了B2型合金中点缺陷形成的透射动力处理。在构建缺陷模型时，假定：（1）基态下的宪法缺陷是抗岩原子，（2）由于温度升高而引起的缺陷行为可以描述为一种杂种状态，其中RVD反应以及ASAR和其他成功RVD过程的反应仅发生。 Nial和Feal合金的数值结果很好地再现了它们观察到的趋势，例如，Ni（Fe）空位的首选形成以及在系统中以及在feal，RVD和ASAR类似行为中的抗site Al原子的某个创建。它显示出高于49.5％CD的迅速增加，在51.5％的CD时达到约1％，这与B2 Feal合金的结果相当。因此，可以预期点缺陷行为是与feal中类似的混合动力行为。当温度降低时，B2 AUCD合金转换为马氏体相。据信，在马氏体状态下出现的“马氏体衰老效应”与点缺陷行为有关。测量了由于慢冷和液压AU-49.8CD合金，测量了晶格常数的变化以及由于Martensite衰老而引起的基本和超晶体反射的综合强度。结果没有显示可检测的变化，表明空缺迁移和衰老期间的远距离顺序不会发生。这表明在这种合金中，远程顺序对马氏体衰老效应的独立性。较少的