• T A Abinandanan

      Articles written in Bulletin of Materials Science

    • Spinodal decomposition in fine grained materials

      H Ramanarayan T A Abinandanan

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      We have used a phase field model to study spinodal decomposition in polycrystalline materials in which the grain size is of the same order of magnitude as the characteristic decomposition wavelength ($\lambda_{SD}$). In the spirit of phase field models, each grain (𝑖) in our model has an order parameter ($\eta_i$) associated with it; $\eta_i$ has a value of unity inside the 𝑖th grain, decreases smoothly through the grain boundary region to zero outside the grain. For a symmetric alloy of composition, 𝑐 = 0.5, our results show that microstructural evolution depends largely on the difference in the grain boundary energies, $\gamma_{gb}$, of A-rich (𝛼) and B-rich (𝛽) phases. If $\gamma^{\alpha}_{gb}$ is lower, we find that the decomposition process is initiated with an 𝛼 layer being formed at the grain boundary. If the grain size is sufficiently small (about the same as $\lambda_{SD}$), the interior of the grain is filled with the 𝛽 phase. If the grain size is large (say, about 10 $\lambda_{SD}$ or greater), the early stage microstructure exhibits an A-rich grain boundary layer followed by a B-rich layer; the grain interior exhibits a spinodally decomposed microstructure, evolving slowly. Further, grain growth is suppressed completely during the decomposition process.

    • A study of phase separation in ternary alloys

      Saswata Bhattacharyya T A Abinandanan

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      We have studied the evolution of microstructure when a disordered ternary alloy is quenched into a ternary miscibility gap. We have used computer simulations based on multicomponent Cahn–Hilliard (CH) equations for 𝑐A and 𝑐B, the compositions (in mole fraction) of A and B, respectively. In this work, we present our results on the effect of relative interfacial energies on the temporal evolution of morphologies during spinodal phase separation of an alloy with average composition, 𝑐A = 1/4, 𝑐B = 1/4 and 𝑐A = 1/2. Interfacial energies between the ‘A’ rich, ‘B’ rich and ‘C’ rich phases are varied by changing the gradient energy coefficients. The phases associated with a higher interfacial energy are found to be more rounded than those with lower energy. Further, the kinetic paths (i.e. the history of A-rich, B-rich and C-rich regions in the microstructure) are also affected significantly by the relative interfacial energies of the three phases.

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