Abstract: This study investigates how hetero-zone boundaries between soft and hard regions affect strain incompatibility and hetero-deformation-induced (HDI) strengthening in heterostructured metallic materials. We focused on Cu-based alloy (C194)/stainless steel (SS304) clad materials, featuring distinct soft and hard domains separated by a single boundary, to quantify the HDI strengthening. Despite the typical strain incompatibility caused by mechanical incompatibility at the boundary, the precise microstructural characteristics remain unclear. To address this, we varied the initial grain sizes of C194 while keeping the grain size of SS304 constant to explore a relation between strain incompatibility and HDI strengthening. Our results show that HDI strengthening is not directly proportional to the mechanical incompatibility at the C194/SS304 boundary. Additionally, this hetero-zone boundary induces two stages of HDI strengthening during uniform elongation, driven by newly generated α'-martensite due to the TRIP effect. These analyses, supported by both experimental and computational methods, correlate with the evolution of geometrically necessary dislocations at the hetero-zone boundaries. Our findings offer valuable guidance for designing hetero-zone boundaries by considering microstructural features such as grain sizes of each interior component and shapes/morphologies/volume fractions of hetero-zones.

Key words: Heterostructure, Hetero-deformation-induced strengthening, Dislocation-based constitutive model, Geometrically necessary dislocations, Hetero-zone boundary