Microstructure Development in a Magnesium Alloy Tube during Ring Hoop Tension Testing and Warm Gas Forming

The evolution of microstructure in a Mg 3.4%AI-0.16%Zn-0.33%Mn alloy tube was studied during deformation by ring hoop tension testing (RHTT). When the tests were carried out at moderate temperatures and relatively high strain rates, the accompanying c-axis strains were mainly accommodated by twin formation. At temperatures above 200°C and the lowest strain rate (0.001s^-1), the formation of voids in the partially dynamically recrystallized regions caused premature fracture. The microstructural development in hot gasformed samples was similar to that observed during RHTT testing. These results indicate that RHTT testing is an effective way of studying the deformation behavior of Mg alloys during tube gas forming.