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Antiphase Domain Structures and Analytical Electron Microscopy of α-Bainite in a Cu-Zn-Al Alloy.

Published online by Cambridge University Press:  26 February 2011

Y. Hamada ,
C.M. Wayman  and
M.H. Wu
Y. Hamada
Affiliation:
Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois
C.M. Wayman
Affiliation:
Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois
M.H. Wu
Affiliation:
Memry Corporation, Norwalk, Connecticut
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Abstract

Antiphase domain (APD) structures and associated composition analyses of the α l-bainite which forms during isothermal heat-treatment of a Cu-26.7wt%Zn-4.0wt%Al alloy have been examined by TEM dark field imaging and energy dispersive X-ray microanalysis. At an early stage both nearest-neighbor (NN) and next-nearest-neigbor (NNN) APD structures of the β-parent phase are inherited by the α1-bainite having an M18R structure. The EDX analyses indicate that there is a difference in composition between the α 1-bainite and the β-parent phase at this stage in spite of the inheritence of both NN and NNN APD structures. Local depletion of Zn concentration at dislocations is also observed in the parent phase. With increasing aging time, the α 1-bainite grows in a manner that the NN APD structure still remains inherited but the NNN APB structure changes into a NNN disordered structure at outer regions of the plate. In addition, Zn and Al rich regions also form adjacent to the interface in the parent phase. The observed growth of APD structures in association with compositional analyses strongly suggest that the initial bainitic transformation is by a shear mechanism at solute depleted defects although subsequent plate growth is diffusion dominated.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 205: Symposium F – Kinetics of Phase Transformations , 1990 , 177
Copyright
Copyright © Materials Research Society 1992

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