Spinodal Decomposition Non-Classical Nucleation Theory Microstructure Evolution Spinodal Decomposition Non-Classical Nucleation Theory Byeong-Joo Lee POSTECH - MSE calphad@postech.ac.kr
Background Microstructure Evolution Y C Li et al. MSMSE (2012) Feng Yan and John Texter, 2006
Introduction Refs: J.W. Cahn : Acta Met. 7, 795 (1961); J. Chem. Phys. 42, 93 (1965); Trans. AIME, 242, 166 (1968) J.E. Hilliard, "Phase Transformations," ASM (1970) ► Historically, initiated in an effort to explain uniform distribution of CuAl2 precipitates in Al-Cu alloys. ► Consider the Gibbs energy curve and stability of matrix phase against infinitesimal fluctuation of concentration. ○ Region I · stable against small local fluctuation (nothing happens) large fluctuation → nucleation of β small in extend, large in degree, "Nucleation & Growth Mechanism" ○ Region II · unstable against small local fluctuation (decrease in total energy) spontaneously goes to more fluctuation small in degree, large in extend, "Uphill Diffusion", relatively periodic microstructure
Spinodal Decomposition
Mathematical Formulation - Thermodynamics of Spinodal Decomposition
Mathematical Formulation - Thermodynamics of Spinodal Decomposition
Mathematical Formulation - Thermodynamics of Spinodal Decomposition
Mathematical Formulation - Thermodynamics of Spinodal Decomposition ► existence of minimum in wave length : for the balance between bulk energy and interfacial energy