Deformation mechanism of ZK60 magnesium bars during radial forging: Mathematical modeling and experimental investigation

Radial forging (RF) is a multidirectional, simultaneous forging process in which four dies perform pressing operations through high-frequency radial movements. This paper proposes a regionalized, multiscale strain field model to analyze the microstructural characterization of ZK60 Mg alloys during RF. ZK60 magnesium alloy bars were processed under different accumulated strains using RF at 300 degrees C. Based on the theoretical calculation results, the microstructures, texture evolution and mechanical responses of the bars were systematically investigated. The results indicate that twinning dominated the early stages of deformation, while dynamic recrystallization occurred subsequently and dominated further deformation process. At the early deformation stage, a gradient structure was formed owing to the uniform distribution of strain along the radial direction (RD). The grains in various radial parts were gradually refined by increasing the number of RF passes, eventually evolving into a bimodal grained structure including coarse (similar to 16.2 mu m) and fine (similar to 2.1 mu m) grains. Meanwhile, a precipitation difference is formed between coarse grain and DRX grain. The texture of the RFed bars changed as the RF strain increased, and the c-axis of most of the deformed grains rotated in the RD. Furthermore, the basal pole intensity exhibited a decreasing trend, followed by the large-scale nucleation of the dynamic recrystallization. Additionally, superior mechanical properties including higher values of tensile strength (341 MPa) and ductility (27.1%), were achieved after the three passes.

Automated summary

This study investigated the microstructural characterization of ZK60 magnesium alloy during radial forging, finding that twinning dominated the early stages of deformation followed by dynamic recrystallization. By increasing the number of RF passes, the grains gradually refined and eventually evolved into a bimodal grained structure. Superior mechanical properties were achieved after three passes, including higher tensile strength and ductility.