It was presented the in situ observation of growth behavior and morphology of delta-ferrite as a function of solidification rate in an AISI304 stainless steel. The specimens have been solidified and observed using confocal scanning laser microscopy (CSLM). The δ-phase always appears like cells on the sample surface when critical supercooling occurs, during which the L→δ transformation starts. The solid-liquid (S-L) interface is found to be finger shaped and has no faceted shape. γ phase appears among δ grains due to partitioning of Ni into the melt during solidification, when solidification rate is higher. The mergence of observed δ cells is possible for the steel sample cooled at 7.5℃/min. The formation of dendrites can be observed on the free surface of the steel sample cooled at 150℃/min. The size of solidified delta grains decreases from 120 to 20-80μm, and the volume fraction of solidified austenite increases with increase in solidification rate from 7.5 to 150℃/min. The relation between the tip radius of δ cell and its growth rate is deduced, and the results agree with the experimental values.
介绍了宝钢研究院共焦激光扫描显微镜(Confocal Laser Scann ing M icroscopy,CLSM)的结构及其工作原理,在此基础上通过Fe-C二元合金凝固、奥氏体不锈钢凝固、低碳钢中高温铁素体(δ)奥氏体(γ)相变界面稳定性、AISI304不锈钢加热过程中δ相的形核与生长、AISI304不锈钢冷却过程中δ→γ相变等典型实例描述了CLSM在钢铁相变原位观察中的应用情况。表明CLSM在研究钢铁材料的凝固、固态相变、夹杂运动等方面具有无与伦比的优势与应用前景。
