Abstract
In order to study the basic principles of vibration-excited liquid metal nucleation technology, a coupled model to connect the temperature field calculated by ANSYS Fluent and the dendritic growth simulated by cellular automaton (CA) algorithm was proposed. A two-dimensional CA model for dendrite growth controlled by solute diffusion and local curvature effects with random zigzag capture rule was developed. The proposed model was applied to simulate the temporal evolution of solidification microstructures under different degrees of surface undercooling and vibration frequency of the crystal nucleus generator conditions. The simulation results showed that the predicted columnar dendrites regions were more developed, the ratio of interior equiaxed dendrite reduced and the size of dendrites increased with the increase of the surface undercooling degrees on the crystal nucleus generator. It was caused by a large temperature gradient formed in the melt. The columnar-to-equiaxed transition (CET) was promoted, and the refined grains and homogenized microstructure were also achieved at the high vibration frequency of the crystal nucleus generator. The influences of the different process parameters on the temperature gradient and cooling rates in the mushy zone were investigated in detail. A lower cooling intensity and a uniform temperature gradient distribution could promote nucleation and refine grains. The present research has guiding significance for the process parameter selection in the actual experimental.
Highlights
IntroductionFerritic stainless steel is easy to form developed columnar dendrites during solidification [1]; in the rolling process, it is easy to form a strong texture and this is the main reason for wrinkles, cracks, and other defects [2], which restrict its yield and wide application
Published: 21 March 2021Ferritic stainless steel is easy to form developed columnar dendrites during solidification [1]; in the rolling process, it is easy to form a strong texture and this is the main reason for wrinkles, cracks, and other defects [2], which restrict its yield and wide application.Increasing the ratio of the equiaxed dendrite is an effective method to improve its forming defects
The influence of process parameters on the evolution of solidification microstructures and columnar-to-equiaxed transition (CET) behavior were investigated by coupling the cellular automaton (CA) model with temperature field calculation results
Summary
Ferritic stainless steel is easy to form developed columnar dendrites during solidification [1]; in the rolling process, it is easy to form a strong texture and this is the main reason for wrinkles, cracks, and other defects [2], which restrict its yield and wide application. Han et al [25,26] developed the CA–FE model to reveal the process of dendrite epitaxial nucleation from the substrate and investigated the micro-mechanisms for the axial structure and the curved columnar grain formed in a molten pool of welding. The influence of process parameters (the different degrees of surface undercooling and vibration frequency of the crystal nucleus generator) on the evolution of solidification microstructures and CET behavior were investigated by coupling the CA model with temperature field calculation results. It aims to explore the influence mechanism of process parameters on the solidification microstructure and provide guidance for the actual experimental
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