Evolution of multivariant microstructures with anisotropic misfit: A phase field study

✍ Scribed by Saswata Bhattacharyya; T.A. Abinandanan

• Book ID: 103998683
• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 670 KB
• Volume: 57
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2008.10.008

✦ Synopsis

We study, in two dimensions, the effect of misfit anisotropy on microstructural evolution during precipitation of an ordered b phase from a disordered a matrix; these phases have, respectively, 2-and 6-fold rotation symmetries. Thus, precipitation produces three orientational variants of b phase particles, and they have an anisotropic (and crystallographically equivalent) misfit strain with the matrix. The anisotropy in misfit is characterized using a parameter t = yy / xx , where xx and yy are the principal components of the misfit strain tensor. Our phase field simulations show that the morphology of b phase particles is significantly influenced by t, the level of misfit anisotropy. Particles are circular in systems with dilatational misfit (t = 1), elongated along the direction of lower principal misfit when 0 < t < 1 and elongated along the invariant direction when À1 6 t 6 0. In the special case of a pure shear misfit strain (t = À1), the microstructure exhibits star, wedge and checkerboard patterns; these microstructural features are in agreement with those in Ti-Al-Nb alloys.