Time-dependent nucleation in partitioning transformations

2019-11-07 04:41:23

state rate cluster nucleation dependent

责任者: Kelton, K.F. 单位: Dept. of Phys., Washington Univ., St. Louis, MO, USA 来源出处: Acta Materialia(Acta Mater. (UK)),2000/05/11,48(8):1967-80 摘要: A model is presented and solved numerically for the time-dependent nucleation of a precipitate, coupling the interfacial and long-range diffusive fluxes. The effect of pre-existing cluster distributions is studied. Results from the numerical calculation are compared with those from the classical theory of nucleation. The introduction of coupled fluxes decreases the steady-state nucleation rate and increases the induction time over that from the classical theory, often by several orders of magnitude. The composition of the parent phase near a cluster of the new phase is shifted toward the new phase composition. Such linked-flux nucleation can be important for microstructural control of solid-state precipitation processes, and may explain the formation of the nano-structured composites in some devitrified metallic glasses. Approximate expressions for the situ-dependent cluster growth rate, steady-state nucleation rate and induction time are derived and checked against the results of the numerical calculation 关键词: diffusion;long-range order;metallic glasses;nucleation;precipitation;time-dependent nucleation;partitioning transformations;pre-existing cluster distributions;long-range diffusive fluxes;steady-state nucleation rate;solid-state precipitation processes;devitrified metallic glasses;in situ-dependent cluster growth rate