Cu-Al合金におけるβ<SUB>1</SUB>→β<SUB>1</SUB>′マルテンサイト変態の現象論的解析

Abstract

Theoretical analysis of martensitic transformations from cubic to long period stacking order structures is presented and applied to the martensitic transformation from β1 (ordered structure of Fe3Al type) to β1′ (18R structure) in Cu-Al alloy. The theoretical analysis has shown that the habit plane normal, the direction and amount of shape deformation in the transformation from cubic to the structure with long period stacking order are the same as those in the transformation from cubic to a hypothetical fcc or fct structure (the structure with long period stacking order from which the regularly arrayed stacking faults are removed), if the stacking faults lie in the basal planes of the martensite with long period stacking order. Thus, the habit plane normal, and the direction and amount of the shape deformation in the transformation from β1 to β1′ in Cu-Al alloy can be estimated by the phenomenological theory that regards the transformation as that from the bcc to the fcc structure. The theoretical results are in good agreement with the available experimental data.The martensite with long period stacking order of the R type has two kinds of stacking faults which are called the cubic and hexagonal type. The phenomenological theory predicts that there should be a linear relationship between α and β which represents the stacking fault probabilities of the cubic and hexagonal type, respectively. In the case of β1′ in Cu-Al alloy, the theoretical value of (1−α)⁄(1−β) is 1.141, corresponding to the experimental value, 1.227.