High ductility and strong work-hardening behavior of Zn modified as-hot-rolled Al–Mg sheets

Abstract

High ductility combining with relative high strength is of great significance for the application of Al–Mg alloys. In this study, excellent ductility and moderated strength are obtained in the as-hot-rolled Al-9.2Mg-0.5Zn sheet, with ultimate tensile strength (σb), yield tensile strength (σ0.2) and elongation (δ) are respectively 434 ± 5 MPa, 228 ± 2 MPa and 48 ± 2%. High ductility of the as-hot-rolled Al-9.2 Mg-xZn (0-1.5 wt%) sheets can be ascribed to their strong work-hardening abilities, which increase firstly and then decline with higher Zn content. The highest work-hardening component (n), work-hardening capacity (Hc) and the initial work-hardening rate (θ0) in the Al-9.2Mg-0.5Zn sheet are 0.428, 1.793 and 3496 MPa, respectively. The microstructures of the Al–Mg–Zn sheets are characterized by electron backscattered diffraction (EBSD), transmission electron microscope (TEM), X-ray diffraction (XRD) and scanning electron microscope (SEM). Low density of pre-existing dislocations (PDs), random grain orientations and reduced stacking fault energy (SFE) contribute to the strong work-hardening capacity and lead to desirable ductility in the as-hot-rolled Al–Mg–Zn sheets. However, numerous precipitates with an uneven distribution are harmful for work-hardening and thus lead to the reduced ductility in the Al–Mg sheet with high Zn content.