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摘要
In general three dissipative processes have to be considered during solid/solid diffusive phase transformations; diffusion in the bulk phases, rearrangement of the crystal lattice and diffusion in the interfacial region. It is evident that different length scales (the thickness of the interface is small compared to the grain size) and time scales (the diffusion across the interface is fast compared to the diffusion in the bulk materials) make it difficult to solve this problem numerically. Instead of solving the coupled interface migration and diffusion equations it is advantageous to set up appropriate, parameter dependent shape functions describing mole fraction profiles. The time dependent evolution of the parameters of these shape functions can be derived by means of the thermodynamic extremal principle. Four independent parameters suffice to describe the transformation kinetics in the case that diffusion of the components is fast in the product phase compared to diffusion of components in the parent phase. Based on this new method the kinetics of the gamma/alpha phase transformation in the Fe-rich Fe-Ni system is simulated. The influence of the thickness of the interface and the mobility of the interface on transformation kinetics is studied systematically. The transformation arrives at a steady state (typical for massive transformation) in the a-single phase region, whereas equilibrium is finally attained in the alpha + gamma two-phase region.
- 出版日期2011-6
