The project belongs to the interdisciplinary field of new materials and forensic science. Fingerprints have the characteristics of invariance and uniqueness, playing a key role in the investigation of criminal cases. In criminal investigation techniques, fingerprint visualization technology has always been a focus of research. The magnetic powder method is the most commonly used technique for visualization. Currently, we use standardized magnetic powders produced abroad, which are expensive and lack research on the impact of magnetic powder structure and magnetic properties on fingerprint visualization effects. The market lacks simple preparation processes for fingerprint visualization magnetic powders that are easy to operate, highly sensitive, and adaptable. The absence of high-performance fingerprint visualization materials has become an important factor restricting the development of forensic science and evidence in China. Therefore, how to achieve high precision in fingerprint visualization, convenience in preparation and use, and broad adaptability is a pressing issue that needs to be solved in current research on fingerprint visualization powder materials. Supported by the National Natural Science Foundation, Shanghai Public Security Bureau, and Shanghai Institute of Criminal Science and Technology, this project aimed to address significant national public safety needs. By combining supersonic atomization with solid-state diffusion metallurgy, it conducted a detailed study on the relationship between the structure, magnetic properties, and fingerprint visualization effects of iron-based soft magnetic alloy composite powders. The project successfully developed high-performance fingerprint trace revealing iron-based alloy composite magnetic powders, achieving successful application in different criminal investigation scenes nationwide. This improved the collection rate of fingerprints at crime scenes and the success rate of solving cases, resulting in very significant social benefits. The main work and innovative achievements are as follows: To address the issues of large particle size, uneven size distribution, and poor powder flowability in existing fingerprint revealing powder materials, an alloy powder supersonic atomization device was independently designed and developed. A series of iron-based alloy powder materials with adjustable particle size, uniform size distribution, and good fluidity have been prepared. This has solved the key technical difficulties in the large-scale production of high-performance fingerprint revealing magnetic powders for criminal investigation scenes, and successfully applied these powders in the field of fingerprint revealing at crime scenes. A principle based on hydrogen bond interaction for fingerprint revealing has been proposed, and a doping control strategy for fingerprint revealing iron-based magnetic composite powders has been established. A series of high-performance, low-cost iron-based magnetic composite powders have been developed, which have solved the key technical problems faced in the process of fingerprint revealing at crime scenes, such as poor binding force between the revealing powder and fingerprint traces, high operational technical requirements, and poor contrast ratio. This has achieved the large-scale application of iron-based magnetic composite powders nationwide at crime scenes. The first magnetic composite powder capable of achieving high-precision fingerprint display on different humid objects was developed, solving the problem that fingerprints are difficult to reveal in the current criminal investigation scene under humid conditions. This has enabled the extraction of fingerprints left on humid objects at various crime scenes, increasing the collection rate and case solving rate of fingerprints at criminal investigation sites. According to new appraisal, the research results fill a domestic gap and reach the international advanced level. The project has authorized 7 invention patents, published 6 papers included in SCI journals, trained 15 research talents for fingerprint trace display using magnetic powder, and established the first fingerprint powder display material and technology research team oriented towards practical needs of criminal investigation. The achievements have been successfully applied at nearly a thousand case scenes across more than twenty provinces and cities nationwide, including Shanghai, Jiangsu, Zhejiang, Guangdong, Anhui, Fujian, Hebei, Xinjiang, and Tibet. Through the implementation of this project, Breaking the technological monopoly in the field of trace evidence display at criminal investigation scenes abroad has solved the 'choke point' issue, effectively improving the technological development level of China's criminal investigation fingerprint display field. It has increased the collection rate of fingerprints at crime scenes and the rate of solving cases, struck down the arrogance of criminals, maintained social public safety, and laid a talent foundation for the technological development of China's criminal investigation fingerprint display field, resulting in significant social benefits.