###### Abstract
It has a great influence on the growth and crystallization processes of crystals in the melt, and it also determines the microstructures and the kinetic properties of phase transitions during solidification. By studying the process of solidification and the formation of solid-liquid interfaces, we can grasp the regularities of crystallization and control the formation of material solidification structures, distribution of components, and changes in structure. This provides a theoretical basis for obtaining high-quality space materials. Observation of the solid-liquid interface morphology of high-temperature materials in space enables the analysis and study of many problems arising during solidification. Therefore, processing X-ray images of the melting and solidification processes allows researchers to visualize the crystal growth process more intuitively [5; 6]. Histogram equalization algorithms achieve visual enhancement of images by redistributing the gray level distributions of image pixels, but the algorithms have shortcomings such as loss of image details and over-enhancement. In order to overcome these drawbacks, improved histogram equalization methods have emerged, such as Adaptive Histogram Equalization (AHE) and Contrast Limited Adaptive Histogram Equalization (CLAHE). AHE and CLAHE perform histogram equalization based on local features of the image. They divide an image into smaller regions and then carry out independent histogram equalization for each image region in order to preserve the local details of the image. CLAHE, based on AHE, introduces a contrast-limiting mechanism to avoid over-enhancement. However, these histogram equalization algorithms do not fully consider the information of neighboring regions of each pixel during contrast enhancement, which will generate noise in the output image. To solve these problems, [PERSON] and [PERSON] [7] proposed a dual-sub-image equalization algorithm based on histogram modification. This algorithm enhances the image contrast without losing the details of the image and also maintains the brightness of the image. However, it results in distortion of the enhanced image when the gray level probability distributions of the two sub-images are uneven. [PERSON] et al. [8] put forward a contrast enhancement method based on adaptive histogram correction and equalization. The method combines adaptive histogram correction and histogram equalization and effectively reduces artifacts and insufficient local detail enhancement caused by traditional methods. In addition, there have been many variants of the CLAHE and AHE that address the characteristics of low image contrast and blurry images. For example, [PERSON] et al. [9] used CLAHE and adaptive color correction methods to address the problem of blurred underwater images caused by limited available light, low resolution, and regular cameras. [PERSON] et al. [10] proposed a bi-histogram equalization algorithm with adaptive image correction to solve the problems of image brightness bias, image over-enhancement, and gray level merging that occur in traditional histogram equalization algorithms. Although the above image contrast enhancement algorithms can effectively enhance the details of the darker parts of the image, the details of the brighter parts of the original image are often not enhanced but even weakened. By considering the possible small brightness differences of low-contrast X-ray images, this paper designed a Gradient Three-Interval Equalization algorithm combined with Improved Adaptive Contrast Enhancement(GTIE-IACE) suitable for X-ray image enhancement of high-temperature material experiments, so that the details of both the darker and brighter parts of an image can be effectively enhanced and preserved, and the changes in the solid-liquid interfaces during melting and solidification of high-temperature materials can be clearly observed. This study is based on experimental images from ground laboratories. It is planned to conduct experiments on BiFeO\({}_{3}\) materials on CSS in 2024.