In-situ Observation of Engulfment and Pushing of Small Particl in Molten Metal by Advancing Melt/Solid Interface

用共聚焦激光扫描显微镜对钢液/固界面推进过程中夹杂物颗粒的卷入或推挤进行了原位研究。当界面前进速度超过某一临界值时，钢液中的固态氧化铝团簇颗粒或液态硅酸盐/铝酸盐球状颗粒会被界面吞没，并向颗粒凸起，形成凸起。在较低的速度或较小的半径，在这两个类中的颗粒被推的界面，不形成凸块。凸块的形状是合理地再现了从熔体穿过颗粒的界面的热传递的二维有限元分析。中间粒子引起的热传递减少被认为是导致吞没的原因。根据枝晶间凝固速率和empi的估计，在凝固过程中，较小的氧化铝夹杂物没有被截留在枝晶固体中。 关于我们 凝固钢对氧化铝夹杂物的吞没的统计数据。然而，凝固过程中枝晶间液体中氧和硫的浓度梯度增强了枝晶间液体的吞噬。这些元素在钢液/Al 2 O3界面上具有表面活性，并在枝晶间Al 2 O3夹杂物上产生很强的毛细作用力，在低碳钢中观察到δ-铁素体/γ-奥氏体相变。测量了一个高能δ/δ晶界和两个不相干的δ/γ界面的三相点的二面角。从观察到的二面角的平均值，γ/δ非相干的自由能。讨论了低硫钢的d/g边界对非相干的二面角和自由能的影响。原子同时还研究与讨论用成分过冷理论和不稳定性理论对γ相枝晶生长进行了观察和分析。这表明观察结果与理论之间有很好的一致性。少

Engulfment or pushing of inclusion particle by advancing melt/solid interface of steel has been investigated in-situ with a confocal scanning laser microscope. When the velocity of advancing interface exceeds a critical value for a particle, solid alumina cluster particle or liquidsilicate/aluminate globular particle in steel melt is found engulfed by the interface which extends in a convex way to form a bump toward the particle. At lower velocities or for smaller radii, the particles in both classes are pushed by the interface which does not form the bump. The shape of the bump is reasonably reproduced by a two-dimensional FEM analysis of heat transfer from the melt across the particle to the interface. Reduced heat transfer caused by the intervening particle is considered responsible for the engulfment.We also show that. the smaller alumina inclusions are not entrapped in the dendritic solid during solidification, based on estimates of the interdendritic solidification rates and empi … More rical data on the engulfment of alumina inclusions by solidifying steel. Engulfment by the interdendritic liquid however is enhanced by the gradients of the concentrations of oxygen and sulfur in the interdendritic liquid during solidification. These elements are surface active on the liquid-steel/alumina interface and m turn introduce very strong capillary forces on the interdendritic alumina inclusions.Phase transformation of delta-ferrite/gamma-austenite in low carbon steels was observed. Dihedral angles at triple points of one high energy delta/delta grain boundary and two incoherent delta/gamma interphase boundaries were measured. From the average value of observed dihedral angles, free energy of gamma/delta incoherent. boundary for a steel with low sulfur content on the dihedral angle and free energy of incoherent, d/g boundary were discussed. At. the same time. the dendritic growth of gamma-phase was observed and analyzed by the constitutional supercooling and instability theories. which show good agreement between the observations and theories. Less