The crystallography of martensite transformations III. Face-centred cubic to body-centred tetragonal transformationsLa cristallographie des transformations martensitiques III. Les transformations du système cubique à faces centrées en tétragonal centréDie kristallographie der martensit Transformationen. III. Transformationen von kubisch-flächenzentrierten zu tetragonalraumzentrierten gittern
Abstract
The theory developed in Parts I and II is applied to transformations from face-centred cubic to body-centred tetragonal in the alloys Fe-C, Fe-Ni, Fe-Ni-C. The theoretical predictions of habit planes, orientation relationships and directions of the homogeneous strain are found to be in satisfactory agreement with all the available experimental data. Thus, the hypothesis that the inhomogeneous shear is a part of the twinning shear in the final structure has been substantiated for the transformations considered.
The habit plane interface envisaged by Frank is shown to be a special case of the type of interface expected on the present theory: all planes in the zone of the invariant line, and in particular the twinning plane, meet edge to edge in the interface.
Résumé
La théorie développée dans les Parties I et II est appliquée aux transformations du système cubique à faces centrées en tetragonal centré, dans les alliages Fe-C, Fe-Ni, Fe-Ni-C. Il est constaté que les prédictions théoriques des plans limites, des relations d'orientation et des directions de déformation homogène sont en accord satisfaisant avec toutes les données expérimentales, disponibles. Ainsi, l'hypothèse que la tension non-homogène fait partie de la tension de maclage dans la structure finale, a été confirmée pour le cas des transformations considérées. Il est montré que l'interface constituée par un plan limite, envisagée par Frank, n'est qu'un cas particulier de l'interface proposée par la présente théorie, à savoir: tous les plans dans la zone de la ligne invariante, et en particulier le plan de maclage, se rencontrent suivant une arête commune dans l'interface.
Zusammenfassung
Die in Teil I und II entwickelte Theorie wird auf die Umwandlungen kubisch-flächenzentriert zu tetragonal-raumzentriert in Fe-C, Fe-Ni und Fe-Ni-C Legierungen angewandt. Die theoretischen Voraussagen über Habitusebenen, Beziehungen der kristallographischen Orientierungen und Richtungen homogener Verzerrungen stimmten zufriedenstellend mit allen vorhandenen experimentellen Angaben überein. Somit ist die Hypothese, dass die inhomogene Scherung einen Teil der Zwillingsscherung in der Endstruktur darstellt, für die hier betrachteten Transformationen bestärkt worden.
Es wird gezeigt, dass die von Franck vorgeschlagene Habitusebenengrenzfläche ein Spezialfall des nach der vorstehenden Theorie zu erwartenden Grenzflächentyps ist. Alle Ebenen in der Zone der invarianten Richtung und im besonderen die Zwillingsebene schneiden sich in der Grenzfläche.
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