The effect of differential roller temperature (DTR) (low and high roller temperature difference: 60 and 180 K) on the microstructure evolution, deformation mechanism, and mechanical properties were investigated in a commercial AZ31B alloy sheet. Compared with the LDTR sample, a considerable shear strain ( 0.4) in the HDTR sample led to a multiple-twinning system, especially the formation of contraction twins (CTWs) and double twins (DTWs). After annealing, the HDTR-annealing (HDTR-A) sample achieved an excellent ductility (∼33.6%) as a result of a higher recrystallization fraction (∼71.75%) and more optimized texture component (max basal texture intensity decrease from 36.13–8.06). GRAPHICAL ABSTRACT IMPACT STATEMENT A new method, differential temperature rolling, was used in AZ31B Mg alloy to induce multiple-twinning systems, which strongly influences the recrystallization mechanism and texture evolution, leading to a high ductility.
Multiple deformed substructures including dislocation cells, nanotwins (NTs) and martensite were introduced in super austenitic stainless steels (SASSs) by cryogenic rolling (Cryo-R, 77 K/22.1 mJ·m−2). With the reduction increasing, a low stacking fault energy (SFE) and increased flow stress led to the activation of secondary slip and the occurrence of NTs and martensite nano-laths, while only dislocation tangles were observed under a heavy reduction by cold-rolling (Cold-R, 293 K/49.2 mJ·m−2). The multiple precursors not only possess variable deformation stored energy, but also experience competition between recrystallization and reverse transformation during subsequent annealing, thus contributing to the formation of a heterogeneous structure (HS). The HS, which consists of bimodal-grained austenite and retained martensite simultaneously, showed a higher yield strength (~1032 MPa) and a larger tensile elongation (~9.1%) than the annealed coarse-grained Cold-R sample. The superior strength–ductility and strain hardening originate from the synergistic effects of grain refinement, dislocation and hetero-deformation-induced hardening.
2 April 2025 in Materials Science and Engineering: A
The effects of secondary rolling on the microstructure evolution and mechanical properties of Al/Mg/Al clad sheets have been investigated. The results indicate that a double-layer intermetallic compound (Mg2Al3 and Mg17Al12) forms and sandwiches the MgO film during the first rolling and annealing, while the sandwich structure shows a low peel strength owing to the intrinsic brittleness of intermetallic. However, a secondary rolling leads to a shear-induced breakage of the sandwich structure, whereupon the peel strength significantly increases from 1.3 N/mm to 12.7 N/mm on account of an effective bonding of the Mg/Al interface. The secondary rolling not only eliminates the influence of MgO on the interface, but also improves the bonding strength of the interface. Furthermore, the clad sheet can obtain an excellent elongation (21%) and remain of high interfacial strength (∼12 N/mm) after the recovery annealing.