Effect of Different Laminate Thicknesses on the Microstructure and Mechanical Properties of 304 Austenitic Stainless Steel/420 Martensitic Stainless Steel Multilayer Composites

This study examines how laminate thickness affects reinforcement mechanisms and mechanical properties in 304 austenitic/420 martensitic stainless steel composites. Through varied 420 layer thickness ratios (A2:1:1, A4:1:2, A6:1:3) and 1050 °C annealing, scanning electron microscope/electron backscatter diffraction/energy‐dispersive spectroscopy analyses reveal interfacial evolution, elemental diffusion, and texture. Tensile tests show thinner 420 layers (A2) effectively enhance tensile strength (700 MPa) and elongation (9.2%) by inhibiting grain coarsening, optimizing dislocation distribution, and increasing low‐angle grain boundaries. Conversely, thicker layers (A6) induce Cr/Ni enrichment (5 μm diffusion width), forming brittle interfacial phases that degrade mechanical properties (strength drops to 209.6 MPa). Postannealing, the R2 specimen achieves superior strength–ductility synergy (1048.7 MPa, 23.5% elongation) via improved interfacial bonding and recrystallization. Fractography confirms that effectively enhanced stress compatibility suppresses crack propagation, boosting energy absorption. These findings establish laminate design and thermal processing as critical levers for high‐performance composites.