Research progress in metallic materials solidification based on synchrotron radiation imaging technology

Solidification is crucial in the preparation of metal materials. The solidification process directly determines the microstructure and macroscopic properties of metal materials. When a metal is transformed from a liquid to a solid state，factors such as the formation and growth of grains，solidification rate，temperature gradient，and alloy composition lead to different microstructures，ultimately defining the final microstructure of the metal. Variations in these factors not only determine the mechanical properties of the metal but can also cause defects such as grain boundary defects， gas pores， and inclusions， etc.，thereby affecting its overall quality and service performance. Due to its high penetration and high spatiotemporal resolution，synchrotron radiation enables the real-time observation and tracking of microstructural evolution during metal solidification， leading to a deeper understanding of the underlying mechanisms. This paper reviews the latest progress of synchrotron radiation imaging technology in the study of the solidification process of metallic materials at home and abroad，with a focus on its application and research achievements in crystal nucleation and growth，the formation mechanism of solidification defects，and rapid solidification （welding and additive manufacturing）. By combining new methods such as phase field simulation and machine learning，researchers have made significant progress in grain refinement mechanisms，the formation laws of pores and hot tearing，and the control of rapid solidification modes. Finally，it is pointed out that improving the temporal and spatial resolution of synchrotron radiation，conducting multi-scale coupling characterization，integrating experiments with numerical simulations，and introducing data-driven intelligent analysis methods are important development directions for in-situ studies of the solidification process in the future. This will provide a more solid theoretical basis and technical support for the design of advanced materials and process optimization.