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On the Shape Evolution of Coherent Precipitates: Discrete Atom Method

Published online by Cambridge University Press:  21 February 2011

Jong K. Lee and
Jun H. Choy
Jong K. Lee
Affiliation:
Department of Metallurgical & Materials Engineering, Michigan Technological University, Houghton, MI 49931
Jun H. Choy
Affiliation:
Department of Metallurgical & Materials Engineering, Michigan Technological University, Houghton, MI 49931
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Abstract

Morphological evolution of coherent precipitates with arbitrary transformation strain is studied via a discrete atom method. With a purely dilatational misfit strain, a soft precipitate tends to have a plate-like equilibrium shape, whereas a hard precipitate takes up a shape of high symmetry such as a circle. If the stiffness is comparable between the matrix and precipitate, however, the equilibrium shape depends on the degree of anisotropy, misfit strain, size, and interfacial energy. Shape bifurcation phenomena from circular to rectangular shapes are also revealed during clustering. With either a tetragonal misfit strain of mixed signs or a pure shear misfit strain, a precipitate takes up a plate-like shape whose major axis lies along the direction containing an invariant line in accordance with the continuum elasticity prediction. Both elastic anisotropy and elastic inhomo-geneity exert little influence on the preferred orientation relationship. With a misfit strain of combined shear and dilatation, a precipitate follows an orientation and shape dictated by both components of the misfit strain.

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