Evolution of multiscale heterostructures and comprehensive properties improvement in the large thickness ratio Ti/Al/Mg clad plates under heterothermal rolling

The preparation process of metal clad plates with large thickness ratios (>20) requires ensuring the substrate thickness while also achieving good mechanical properties, a challenge that traditional rolling processes struggle to meet. In this study, TA1/1060/AZ31 clad plates with large thickness ratios (>40) and engineered heterostructures were fabricated via heterothermal rolling, achieving synergistic enhancements in bonding strength and tensile properties. This is attributed to localized interfacial strain concentration induced by the temperature gradient, and sustained strain hardening within the multiscale heterostructured magnesium matrix. The study reveals that the temperature gradient variation in the normal direction of the matrix causes considerable gradation in its deformation mechanisms and microstructure, resulting in diverse heterostructures. In the hot roller zone, high temperatures and large strains promoted the formation of low-angle grain boundaries (LAGBs) with distinct distribution patterns. In contrast, deformation in the cold roller zone was stress-dominated, where the competition between tensile twins and 〈c+a〉 slip changed at low temperatures. Furthermore, LAGB evolution and 〈c+a〉 slip activity differences caused zone-specific variations in discontinuous dynamic recrystallization (CDRX), affecting dislocation density and grain refinement. The higher CDRX degree in the cold roller zone (soft domain) delayed failure in the hot roller zone (hard domain), while heterogeneities in grain size and texture enhanced strain hardening. The dense presence of 〈c+a〉 dislocations within grains further confirmed the continuous strain hardening behavior. This study provides new insights for the fabrication of metal clad plates with large thickness ratios and the development of novel heterostructures.