LAUSR

Abstract A new type of gradient structure is fabricated by the sequential processing of two advanced severe plastic deformation methods, single-roll angular-rolling and ultrasonic nanocrystalline surface modification, which refine microstructures mainly on the core and surface of a metallic sheet, respectively. This material with a multi-layered grain size gradient in the thickness direction features impressive strength-toughness synergy beyond the initial and reverse gradient-structured materials. The superiority is attributable to hetero-deformation induced mechanisms that originate from microstructural heterogeneity. Ultimately, this work suggests a new processing approach by which a strength-toughness window saturated at a certain level in gradient-structured materials can be extended.