Review: Research progress of gradient nanostructured steels

This review presents a comprehensive critical analysis of Gradient Nanostructured Steels (GNS), systematically examining five key aspects: historical evolution, structural classifications, recent processing methodologies, performance-determining mechanical properties, and governing strengthening mechanisms. By integrating theoretical modeling, advanced characterization, and mechanistic interpretation, the study identifies three fundamental design principles for high-performance GNS: (1) the base matrix must balance strength and ductility; (2) multiscale nanophases should exhibit synergistic strengthening; (3) interfacial cohesion between nanophases and the matrix requires precise optimization. The work concludes by highlighting current challenges hindering widespread adoption and future research directions to enhance industrial scalability and performance reliability—both critical for engineering applications.