Effect of Cooling Rate on AlN Precipitation in FeCrAl Stainless Steel During Solidification

The effect of cooling rate on the evolution of AlN inclusions precipitated during solidification in FeCrAl stainless steel was investigated using an experimental study and thermodynamic and kinetic calculations. The number and size of AlN inclusions precipitated under different cooling rates were examined with the feature function of the field-emission scanning electron microscope. A model combining micro-segregation and the diffusion-controlled growth model was set up to determine the mechanism of AlN particle growth. The results showed that AlN precipitates in the mushy zone. The size of AlN particles decreases and the number of AlN particles increases with increasing cooling rate, whereas the volume fraction is essentially unchanged. The AlN particles grow during solidification after the content of solutes in molten steel has exceeded the concentration in equilibrium with AlN. The nitrogen content varies significantly with the cooling rate during solidification. Increasing the cooling rate and reducing the nitrogen content in the molten steel can reduce the AlN particle size in FeCrAl alloys as the growth time decreases.

通过实验研究以及热力学和动力学计算，研究了冷却速率对铁铬铝不锈钢凝固过程中析出的氮化铝夹杂物演变的影响。利用场发射扫描电子显微镜的特征功能，检测了不同冷却速率下析出的氮化铝夹杂物的数量和尺寸。建立了一个结合微观偏析和扩散控制生长模型的模型，以确定氮化铝颗粒的生长机制。结果表明，氮化铝在糊状区析出。随着冷却速率的增加，氮化铝颗粒的尺寸减小，数量增加，而体积分数基本不变。在钢液中溶质含量超过与氮化铝平衡的浓度后，氮化铝颗粒在凝固过程中生长。凝固过程中氮含量随冷却速率显著变化。随着冷却速率的增加和钢液中氮含量的降低，由于生长时间减少，铁铬铝合金中的氮化铝颗粒尺寸可以减小。