Microstructure and mechanical properties of AZ61 alloys with large cross-sectional size fabricated by multi-pass ECAP

As-cast AZ61 alloys were processed by equal-channel angular pressing (ECAP) using various process parameters. The microstructure and mechanical properties of ECAP-ed and as-cast AZ61 alloys were examined. The results showed that the microstructure of as-cast AZ61 alloys was refined well by ECAP due to dynamic recrystallization caused by ECAP. The mechanical properties of ECAP-ed AZ61 alloys were significantly improved due to the refined microstructure. Fine-grained alloys with large cross-sectional size of 58.2 mm and enhanced mechanical properties were fabricated successfully by ECAP. Extrusion temperature and processing route had an essential effect on the microstructure and mechanical properties. The highest mechanical properties including YS of (218±9) MPa, UTS of (330±10.8) MPa and elongation of (26.9±2.2)% were obtained at 290 °C using processing route BC. Forty-five-degree tensile fracture was found in ECAP-ed AZ61 alloys, which was different from the horizontal fracture occurred in as-cast AZ61 alloys. The fracture of ECAP-ed AZ61 alloys was characterized by ductile fracture due to existence of a large number of dimples as compared to brittle cleavage fracture of as-cast specimens, which was beneficial to enhance the mechanical properties.