Revealing extraordinary strength and toughness of multilayer TWIP/Maraging steels

A series of multilayer TWIP/maraging steels with different states were successfully fabricated by vacuum hot rolling, cold rolling and ageing treatment. The aged multilayer steel has a thicker transition layer than that of hot rolled sample, obtaining a high tensile strength (1163 MPa) and fracture elongation (29%). However, the hot rolled multilayer steel has a superior impact toughness of 152 J/cm2, which is mainly attributed to the obvious interface delamination cracks. The cold rolled multilayer steel contains straight interfaces and equal thick layers, whereas the aged + cold rolled multilayer steel reveals wavy interfaces and uneven layers during the cold rolling process, and the high strength and strain softening of C300 layer result into localized necking and fracture. The hot rolled + cold rolled + aged multilayer steel possesses a extraordinary tensile strength of 1527 MPa and a superior fracture elongation of 21.5%, which is primarily attributed to strengthening mechanisms of nanometer dispersion strengthening, work hardening and grain refining.