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。

• 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
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10650694/
• 关键词: intermetallic compound; B2-type ordered phase; point defect structure; diffraction technique; thermodynamic treatment; FeAl alloys; AuCd alloys; martensite ageing effect; 回折実験; 構造空孔

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

在任何温度和成分下，金属和合金中以稳定状态存在的点缺陷已被证实会强烈影响其材料性能，本研究的目的是通过以下方法确定具有 B2 型有序结构的金属间化合物中的点缺陷结构。通过粉末X射线和中子衍射测量，并通过热力学处理讨论了这些B2型金属间化合物中的缺陷形成机制。B2 FeAl合金的点缺陷测定显示出一定的混合状态，其中四种点缺陷与我们研究小组已经报道的 B2 NiAl 和 CoAl 合金类似，在点缺陷行为中发现了两个奇怪的特征，即随着温度的升高，首先，在 Fe 和 Al 上都会产生热空位。位点（随机空位分布，RVD），其次，反位原子倾向于恢复到自己的位点（反位原子恢复，ASAR）。这些情况永远无法在先前提出的缺陷模型的框架内解释。点缺陷形成B2 型合金中的缺陷模型是基于 Bragg-Williams 方法开发的。在构建缺陷模型时，假设：(1) 基态的结构缺陷是反位原子，(2) 由于温度升高而导致的缺陷行为。被描述为混合状态，其中 RVD 反应和 ASAR 以及 RVD 过程之后的其他反应同时发生。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) 的优选形成。在两个体系中，以及在 FeAl、RVD 和 ASAR 行为中，空位和一定程度的反位 Al 原子的产生。B2 AuCd 合金中的空位浓度作为成分的函数，显示出在 49.5%Cd 和以上时快速增加。在 51.5%Cd 时达到约 1%，与 B2 FeAl 合金的结果相当，因此，点缺陷行为预计与 FeAl 中的混合行为类似。 B2 AuCd 合金在温度降低时转变为马氏体相，马氏体状态时效中出现的“马氏体时效效应”被认为与点缺陷行为以及基本和超晶格反射的积分强度的变化有关。对慢冷和水淬的 Au-49.8Cd 合金进行了马氏体时效的测量，结果没有发现可检测到的变化，表明空位迁移和时效过程中也不会发生长程有序，这表明该合金中的马氏体时效效应与长程有序无关。

项目成果

M. Kogachi: "Point defect behavior in the B2-type intermetallic compounds"High Temperature Materials and Processes. 18. 269-291 (1999)

M. Kogachi：“B2 型金属间化合物中的点缺陷行为”高温材料和工艺。

T. haraguchi, M. Kogachi: "Point defects in B2-type ordered FeAl alloys"Proceeding of International Conference on Solid-Solid Phase Transformations. 521-524 (1999)

T.haraguchi、M.Kogachi：“B2 型有序 FeAl 合金中的点缺陷”国际固-固相变会议录。

M. Kogachi, T. Haraguchi: "Pssibilities of random vacancy distribution and antisite atom recovering in the point defect mechanism in B2-type intermetallics"Intermetallics. 7. 981-993 (1999)

M. Kogachi、T. Haraguchi：“B2 型金属间化合物中点缺陷机制中随机空位分布和反位原子恢复的可能性”金属间化合物。

M.Kogachi and T.Haraguchi: "Random vacancy distribution in B2-type intermetallic compound FeAl"Scripta Mater.. 39. 159-165 (1998)

M.Kogachi 和 T.Haraguchi：“B2 型金属间化合物 FeAl 中的随机空位分布”Scripta Mater.. 39. 159-165 (1998)

M.Kogachi, H.Ishibashi, T.Ohba, X.Ren and K.Otsuka: "Examination of vacancy migration and long-range ordering due to ageing in Au-49.8Cd shape memory alloys."Scripta Mater.. (in press).

M.Kogachi、H.Ishibashi、T.Ohba、X.Ren 和 K.Otsuka：“检查 Au-49.8Cd 形状记忆合金中因老化引起的空位迁移和长程有序。”Scripta Mater..（出版中）