Achieving single-pass high-reduction rolling and enhanced mechanical properties of AZ91 alloy by RD-ECAP pre-processing

Abstract

It is widely recognized that rolling Mg alloys is difficult due to their poor ductility. Conventional rolling of Mg alloys often needs to be conducted at high temperatures with multi-pass small thickness reduction, and the strong basal texture often leads to poor ductility and plate cracking. Herein, we conducted a single-pass high-reduction rolling (SPHRR) on AZ91 alloy after pre-homogenization (PH) and RD-ECAP pre-processing (PH + ECAP). Results shows that the AZ91 rolled plate processed by SPHRR (PH + ECAP + R) exhibits a good combination of high tensile strength (ultimate strength of ~420 MPa, yield strength of ~335 MPa) and high ductility (elongation-to-failure of ~19%), together with significantly reduced edge cracks. Microstructure examinations revealed that the improved mechanical property is mainly attributed to a typical bimodal grain structure featured with relatively high Schmidt factors of basal slips (SF basal ). The fine-grain structure produced by the high-pass RD-ECAP pre-processing contributes to the improvement of formability, provides favourable conditions for dynamic recrystallization (DRX) in further rolling and also promotes the formation of the bimodal structure. Overall, the high-pass RD-ECAP is applicable to improve plastic formability of hard-to-deform materials like Mg alloys, and thus has a promising prospect for industrial applications.