Microstructure Evolution Spinodal Decomposition NonClassical Nucleation Theory ByeongJoo

Microstructure Evolution Spinodal Decomposition Non-Classical Nucleation Theory Byeong-Joo Lee POSTECH - MSE calphad@postech. ac. kr Byeong-Joo Lee www. postech. ac. kr/~calphad

Background Microstructure Evolution Y C Li et al. MSMSE (2012) Feng Yan and John Texter, 2006 Byeong-Joo Lee www. postech. ac. kr/~calphad

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 Cu. Al 2 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 Byeong-Joo Lee www. postech. ac. kr/~calphad

Spinodal Decomposition Byeong-Joo Lee www. postech. ac. kr/~calphad

Mathematical Formulation - Thermodynamics of Spinodal Decomposition Byeong-Joo Lee www. postech. ac. kr/~calphad

Mathematical Formulation - Thermodynamics of Spinodal Decomposition ► existence of minimum in wave length : for the balance between bulk energy and interfacial energy Byeong-Joo Lee www. postech. ac. kr/~calphad