The group standard "Powder Metallurgy Aluminum Matrix Composite Wheel-Mounted Brake Discs for Urban Rail Transit Vehicles," jointly drafted by Hunan Xiangtou Light Materials Technology Co., Ltd. and Guangzhou Metro Group Co., Ltd., has been reviewed and approved by the Standardization Technical Committee of the China Communications and Transportation Association and officially released. The standard applies to urban rail transit vehicles with operating speeds not exceeding 120 km/h and systematically specifies terminology and definitions, environmental and operating conditions, technical requirements, inspection methods, inspection rules, and requirements for marking, packaging, transportation, and storage, covering the entire process. Brake discs for urban rail vehicles of other speed levels may refer to this standard for implementation. Brake discs are key unsprung components of rail transit vehicles, and their lightweight level directly affects traction energy consumption, wheel-rail wear, and ride quality. Traditional cast iron brake discs are difficult to meet the technical upgrading needs in terms of weight reduction, thermal conductivity, and wear resistance. Powder metallurgy aluminum matrix composites, with advantages such as high specific strength, high thermal conductivity, and wear resistance, are gradually entering engineering applications. Although preliminary applications have been made in this field in China, there is a lack of unified technical specifications and quality evaluation systems, leading to uncertainties in product selection, large-scale production, and engineering applications. Light Materials Technology has been deeply engaged in the field of aluminum matrix composites for more than 10 years. Its related products have been awarded "Hunan Province's 100 Key Industrial New Products," selected for the recommended list of independent equipment of the China Urban Rail Transit Association, and achieved the industry's first full-formation mass production application in domestic subways. This standard provides an authoritative technical basis for the product development, production, and engineering application of powder metallurgy aluminum matrix composite brake discs, breaking the long-standing lack of unified technical specifications in China's aluminum matrix composite brake disc field. As an important branch of metal matrix composites, the standardization of brake disc products of powder metallurgy aluminum matrix composites establishes a quality evaluation and inspection rule framework for the application of upstream metal powders in lightweight scenarios of rail transit.