Research on the recrystallization behavior, strengthening and toughening synergy, and fracture mechanisms of multi-layer AZ31 composite sheets using single-pass large-strain rolling techniques

Abstract

In this study, we utilized single-pass large-strain rolling technology to successfully fabricate multi-layered AZ31 magnesium alloy composite sheets with excellent mechanical properties. Using SEM analysis, large-area EBSD stitching tests, and tensile experiments, we systematically investigated the microstructure evolution, recrystallization behavior, structure-performance response mechanism, and fracture mechanism of the composite sheets. The results of our research revealed that the degree of recrystallization in the material increases with the number of composite layers, primarily driven by twinning-induced recrystallization. With five layers, the sheets achieve optimal overall mechanical performances, with a tensile strength of 258 MPa, an elongation rate of 22.7 %, and a strength-ductility product of 47.2 MPa%. Furthermore, we ascertained that the main fracture mechanism is ductile fracture. Calculations showed that the primary strengthening mechanisms are grain refinement, dislocation strengthening, and texture strengthening. Of these, dislocation strengthening exerts the greatest influence on enhancing material performance. The findings of this research demonstrate the feasibility of using single-pass large-strain rolling for producing multi-layered AZ31 magnesium alloy composite sheets. Besides, this paper also offers valuable theoretical and technical references for producing fine-grained, high-strength magnesium alloys.