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Mechanism of atomic diffusion in nickel-based intermetallic compounds of L1_2-type

L1_2型镍基金属间化合物中原子扩散机理

基本信息

批准号：
11650680
负责人：
NUMAKURA Hiroshi
金额：
$ 2.43万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650680/
关键词：
intermetallic compounds order-disorder alloys intrinsic point defects diffusion mechanism shared autonomy electrical resistivity degree of order order-disorder transformation 規格格子合金

项目摘要

The mechanism of atomic diffusion in Ni_3Al, Ni_3Ga and Ni_3Ge has been studied by examining the thermodynamic properties of these materials, most importantly the concentrations of intrinsic point defects, using various experimental techniques.The hypothetical order-disorder transformation temperature of Ni_3Al has been evaluated from the transformation temperatures of a series of alloys Ni_3 (Al, Fe). The transformation temperatures have been determined by in situ measurements of electrical resistivity, and extrapolation to zero Fe content gives 1721 ± 34 K as the transformation temperature of Ni_3Al. This value is in good agreement with the value 1680-1740 K deduced from an analysis of thermodynamic activity data using the results of Monte-Carlo simulation. We proposed earlier an atomistic model of diffusion, where both Ni and Al atoms are assumed to migrate in the crystal primarily by the vacancy mechanism in the sublattice for Ni atoms (the α sublattice vacancy mechanism) ; the mod … More el can reasonably explain the diffusivities of Ni and Al in Ni_3Al. In that discussion, which is based on a pair interaction model of thermodynamic properties, the value of the effective interaction energy between atoms is most critical. The transformation temperature is physically equivalent to the effective interaction energy, and thus the value obtained in this investigation substantiates the discussion made earlier.The thermodynamic activity of components has been measured for Ni_3Ga and Ni_3Ge by solidelectrolyte electromotive-force method. For Ni_3Ga, the effective interaction energy has been determined to be 0.101 ± 0.002 eV from the variation of the activity with composition. The concentrations of point defects and the thermodynamic factor for chemical diffusion have been estimated with the aid of a thermodynamic model, and on their basis the mechanism of diffusion has been examined. The data of tracer diffusion and chemical diffusion for this compound can also be accounted for by the α sublattice vacancy mechanism.The method of activity measurements employed has turned out inappropriate for Ni_3Ge. To resolve the problem, knowledge of the details of the Ni-Ge-O ternary phase diagram is required but is not available at the moment. This is the task left to the future. Thus, no reliable value of the effective interaction energy in this compound has been obtained. Nevertheless, it has been shown that the diffusion behavior in this compound can be understood in terms of the α sublattice vacancy mechanism, if the interaction energy is assumed to be as high as 1.5eV.The α sublattice vacancy mechanism is thus a most plausible mechanism of diffusion for this class of materials. Less

通过对Ni_3Al、Ni_3Ga和Ni_3Ge材料的热力学性质（主要是本特征点缺陷的浓度）的研究，研究了Ni_3Al、Ni_3Ga和Ni_3Ge中原子扩散的机理。从一系列Ni_3 （Al, Fe）合金的相变温度出发，对Ni_3Al的有序-无序相变温度进行了假设。通过原位电阻率测量确定了Ni_3Al的转变温度，外推到铁含量为零时，Ni_3Al的转变温度为1721±34 K。这个值与利用蒙特卡罗模拟结果对热力学活动数据进行分析所得的1680-1740 K值很吻合。我们先前提出了一种原子扩散模型，其中假设Ni和Al原子主要通过Ni原子的亚晶格空位机制（α亚晶格空位机制）在晶体中迁移；该模型可以合理地解释Ni_3Al中Ni和Al的扩散系数。在基于热力学性质的对相互作用模型的讨论中，原子间有效相互作用能的值是最关键的。转变温度在物理上等同于有效相互作用能，因此本研究得到的值证实了前面的讨论。采用固体电解质电动势法测定了Ni_3Ga和Ni_3Ge组分的热力学活性。根据活性随组分的变化，确定Ni_3Ga的有效相互作用能为0.101±0.002 eV。利用热力学模型估计了点缺陷的浓度和化学扩散的热力学因子，并在此基础上对扩散机理进行了研究。该化合物的示踪剂扩散和化学扩散数据也可以用α亚晶格空位机制来解释。所采用的活度测量方法已被证明不适用于Ni_3Ge。为了解决这个问题，需要了解Ni-Ge-O三元相图的细节，但目前还没有。这是留给未来的任务。因此，没有得到该化合物有效相互作用能的可靠值。然而，如果假设相互作用能高达1.5eV，则表明该化合物的扩散行为可以用α亚晶格空位机制来理解。因此，α亚晶格空位机制是这类材料最合理的扩散机制。少