Prediction of precipitate morphology by atomic matching model and FEM analysis with consideration of anisotropy elastic strain in a BCC/HCP system

Abstract

This study focuses on the entire shape of the α precipitate in Ti-22V-4Al in terms of the interphase and elastic strain energies generated between the precipitate and matrix. In order to consider a transformation strain, the volumetric strain and strain relaxation by a misfit dislocation on the interphase boundary are calculated. Firstly, the atomic matching model is employed for determining the preferred habit planes by evaluating the results of geometrical atomic matching. Subsequently, the precipitate configuration that consists of the preferred habit plane is determined by the elastic strain with the minimum value. Then, the elastic strain surrounding and within the predicted precipitate is examined by an FEM analysis, which can be used to calculate the anisotropic elastic strain depending on the shape of the precipitate. A comparison of these results with regard to the precipitate observed by TEM elucidates the determination of the ideal shape of the precipitates in BCC/HCP systems; the optimum configuration of the precipitate that consists of the preferred habit plane is determined by the tradeoff relationship of two factors; one is the strain relaxation due to an increment in the broad face plane, and the other is the decrease in the total elastic strain as the surface ratio approaches a regular square. © 2008 The Japan Institute of Metals.