Simulation of Gas-Atomized T15 High-Speed Steel Solidification Microstructure Using CAFE Model
摘要
The extremely high cooling rates (up to 105 K/s) in gas atomization pose a challenge for experimentally capturing dynamic microstructural evolution. To address this, the solidification of gas-atomized T15 high-speed steel powder was simulated using a cellular automaton–finite element (CAFE) model. The microstructural evolution was investigated under two distinct conditions: (1) as a function of particle size (20–250 μm), where the cooling rate varies passively according to size-dependent heat transfer; and (2) with the cooling rate (0.292 × 105–13.8 × 105 K/s) as an independent variable at a fixed particle size. Increasing particle size leads to a decrease in average aspect ratio but an increase in average grain diameter and secondary dendrite arm spacing (SDAS). In contrast, when the cooling rate is independently increased, the proportion of equiaxed grains rises, while the average aspect ratio, grain diameter, and SDAS decrease. Experimental observations of powders with different sizes confirm the presence of columnar, equiaxed, and mixed structures, and show good agreement with the simulated trends. This study clarifies the distinct roles of particle size and cooling rate in microstructural evolution and provides a theoretical basis for microstructure control in gas atomization.