Numéro
J. Phys. Colloques
Volume 43, Numéro C4, Décembre 1982
ICOMAT-82
International Conference on Martensitic Transformations
Page(s) C4-551 - C4-556
DOI https://doi.org/10.1051/jphyscol:1982486
ICOMAT-82
International Conference on Martensitic Transformations

J. Phys. Colloques 43 (1982) C4-551-C4-556

DOI: 10.1051/jphyscol:1982486

MORPHOLOGY OF LATH MARTENSITE FORMED FROM DEFORMED AUSTENITE IN 18% Ni MARAGING STEEL

I. Tamura, K. Tsuzaki et T. Maki

Department of Metal Science & Technology, Faculty of Engineering, Kyoto University, Sakyo-ku, Kyoto, 606, Japan


Abstract
The change in the morphology of lath martensite with deformation of austenite (ausforming) has been studied by using an 18 % Ni maraging steel. Specimens in austenitic state were deformed in tension by several strains (true strain ε = 0.1 ˜ 1.0) at 773 K (which was above Md temperature). In the case of conventionally quenched (not-deformed) specimen, an austenite grain contained several packets and each packet was almost completely partitioned by parallel blocks. However, this morphology of packets and blocks was markedly changed when martensite was formed from deformed (work-hardened) austenite. The packet size was increased with an increase in the amount of deformation. On the other hand, block width was decreased with an increase in the amount of deformation (up to about ε = 0.2) and blocks became wavy or finely segmented when austenite was heavily deformed (ε = 0.4˜1.0). From the observation of the formation process of lath martensite by applying the Greninger-Troiano heat treatment, it was found that laths with the same habit plane (one of four {111}γ habit planes) were preferentially formed in an austenite grain when the specimen was deformed before transformation, although four {111}γ martensite habit planes were almost evenly observed in an austenite grain in a conventionally quenched specimen. Because of such a restriction of the variant of martensite habit plane, the ausformed lath martensite exhibits the characteristic morphology.