The austenitization of low alloy steels during rapid heating processes was involved in many kinds of advanced heat treatment technologies. Most of the previous research on the austenitization kinetics was focused on the spherical pearlite microstructures, which were different from the lamellar pearlite microstructures. In the present research, to predict the non-isothermal austenitization process of an Fe-C-Cr steel with lamellar pearlite, a novel 3-dimensional (3D) cellular automata model, which considered the influences of the coupling diffusion of Cr and C, and the interfacial diffusion between pearlite lamellae and the pearlite lamellar orientation, was established based on the thermodynamic equilibrium data obtained from the Thermo-Calc software and the simulation results of the DICTRA module. To clarify the influences of the heating rate on the austenitization kinetics and validate the simulation results, the austenitization processes of a Fe-1C-1.41Cr steel for different heating rates were studied with a series of dilatometric experiments. The good agreements between the cellular automata simulation results and the experimental results showed that the newly proposed cellular automata model is reasonable. The experimental results show an obvious change of the transition activity energies from the low to high heating rates. The transition from partitioning local equilibrium (PLE) to non-partitioning local equilibrium (NPLE) mechanisms was proved with DICTRA simulations. Basing on the simulation results, the influences of the pearlite lamellae orientation on the austenitization kinetics and the topological aspects of austenite grains were evaluated. In addition, the topological aspects of the rapidly austenitized grains were also compared to the normal grains.

A cellular automata model was established to simulate grain coarsening processes pinned by second-phase particles. The influences of particle coarsening, precipitation, growth and dissolution, which contain complex changes of size and number density of the particles, on the grain coarsening kinetics were investigated by considering the following two factors: average pinning force per particle and particle number density. The simulation results showed that the average pinning force per particle was related to the particle size, but little influenced by the particle number density. The investigations about the grain boundary/particles interactions showed that the increase of number fraction of particles, which located at the grain boundary junctions, should be the reason for the increase of average pinning force per particle. Then the limiting grain size was researched and compared to the results of some other models. The results showed that the average number of particles to stagnate a grain was related to both the number density and size of particles. At last, the comparisons between the present simulation results and the other simulation and experimental results showed that the present models were efficient in simulating the grain coarsening processes pinned by second-phase particles.

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