###### Abstract  
High-Temperature Materials Science Experiment Cabinet on the Chinese Space Station is mainly used to carry out experimental research related to high-temperature materials science in microgravity. It is equipped with an X-ray transmission imaging module, which is applied to realize transmission imaging of material samples under microgravity. However, the X-ray light source is far away from the experimental samples, and the images obtained by the module are blurred, so it is impossible to accurately observe the morphological changes during the melting and solidification processes of high-temperature materials. To address this issue, this paper proposed a contrast enhancement algorithm specifically designed for X-ray images obtained during the experiments of high-temperature materials. The algorithm is based on gradient three-interval equalization, and it is combined with a Gaussian function to expand the gradient histogram. Meanwhile, the local gray level information within each gradient interval is corrected by designing an improved adaptive contrast enhancement algorithm. By comparing with Adaptive Histogram Equalization (AHE) and Contrast Limited Adaptive Histogram Equalization (CLAHE) algorithms, EnlightenGAN, and Wavelet algorithms, the Contrast Enhancement based contrast-changed Image Quality measure (CEIQ) and Measure of Enhancement (EME) are improved by an average of 56.97%, 10.58%, and Measure of Entropy (MOE) are improved by an average of 7.74 times. The experimental results show that the algorithm makes the image details clearer on the basis of image contrast enhancement. The solid-liquid interface in the image can be clearly observed after contrast enhancement. The algorithm provides strong support for the study of interface dynamics during the experiment process of high-temperature materials. image contrast enhancement; gradient three-interval equalization; improved adaptive contrast enhancement; space materials science experiment Xinze  
growth in microgravity environments and the differences in ground environments, providing a theoretical basis for the preparation of new materials. High-Temperature Materials Science Experiment Cabinet (HTMSEC) on the Chinese Space Station (CSS) is used for experimental research related to high-temperature materials science in microgravity. The X-ray transmission imaging module in HTMSEC can realize dynamic real-time imaging and observation of the melting and solidification processes of materials to examine the morphology and transport efficiency of the solid-liquid interfaces during the opaque phase transitions of high-temperature materials, so as to gain a deeper understanding of the dynamic changes of crystal growth. With the increasing research on the crystal growth of materials, an increasing number of researchers have combined X-rays with space materials science experiments to explore the process and properties of crystal growth by utilizing the penetration and absorption of X-rays. [PERSON] et al. [2] carried out an in situ study of the columnar-to-equiaxed transitions during directional solidification of Al-Cu alloys in microgravity using X-ray. It was found that the solidification rate of the alloy in microgravity is slower, while the grain size is larger, and the columnar crystal region becomes smaller. [PERSON] et al. [3] conducted three series of directional solidification experiments on an Al-20 wt.%Cu alloy at different temperature gradients in a horizontal configuration so as to reduce the effects of gravity-driven phenomena. Real-time in situ characterization was executed using X-ray transmission. Similarly, [PERSON] et al. [4] characterized eGaIn NDs/TPU composite material using field emission Scanning Electron Microscope (SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared spectroscopy (FTIR) techniques. The solid-liquid interface during melting and solidification of a material is a very important physical state.