The formation of an intermediate structure during the dezincification of b Cu?Zn alloys and its relevance for the martensitic transformation

TROIANI; AHLERS

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 1999 p. 200 - 203

0921-5093

The phenomenological theories for martensitic transformation by Wechsler, Lieberman, Read and Bowles, Mackenzie describeswell the crystallography and orientation relationship between austenite and martensite by postulating an undistorted habit plane.However, they do not give information on the actual path of the atomic displacements during the martensitic transformation. Anatomistic model which attempts to do that and results in the same crystallography as in the phenomenological models haspreviously been described for the transformation from the bcc to the fcc structure by one of the authors. In this model the mainshear occurs on the bcc (110)b B11(0 plane, to which a shuffle on an inclined plane is added. Because both steps could neverbe separated experimentally, the model remained speculative. It has now been possible to show that an intermediate structurewhich consists only of shears on (110)b B11(0 can be obtained by the dezincification of b phase Cu?Zn alloys in the form ofcoherent spherical particles with the 4H structure. Its appearance proves that this structure has a sufficiently low free energy toserve also as the first step in the martensitic transformation, in which its energy can be decreased further by the shuffles. © 1999Elsevier Science S.A. All rights reserved.Keywords: Dezincification; Phase transformation; Martensite