부산대학교 도서관

To study the influences of expanding angles on extrusion-shearing-expanding (ESE) process of AZ31 magnesium alloy thin-walled tubes, microstructures and mechanical properties of tubes fabricated by ESE process with different expanding angles 130°, 140°, 150°, respectively, have been investigated by an optical microscope (OM) and an X-ray diffractometer (XRD). The load-stroke curves and equivalent strains changing with different expanding ratios of ESE die structures have been simulated by Deform-3D software. The research results showed that the expanding ratios and expanding angles have great influences on forming loads and equivalent strains, and ESE process can refine the grains of AZ31 magnesium alloy thin-walled tubes effectively, and grain sizes decreased with the dropping of expanding angles. When expanding angle is 140° and the temperature is 380°C, and the expanding ratio is 1.6, the comprehensive mechanical properties of the tubes with yield strength 122.3MPa, tensile strength 288.6MPa, and elongation 15.2% are the best. The texture intensities of AZ31 magnesium alloy were decreased due to the strong shearing force and the dynamic recrystallization (DRX) caused by ESE process. The basal plane of most grains have been deflected relative to the extrusion direction (ED) obviously.