Dynamic tensile properties and microstructural evolution of extruded EW75 magnesium alloy at high strain rates

The dynamic tensile properties and microstructural evolution of an extruded EW75 magnesium alloy deformed at ambient temperature and different high strain rates (from 1000 to 3000 s-1) along extrusion direction (ED) were investigated by Split Hopkinson Tension Bar (SHTB). The corresponding deformation mechanisms, texture evolution and microstructure changes were analyzed by optical microscope (OM), electron backscatter diffraction (EBSD) and transmission electron microscope (TEM). The results show that the extruded EW75 magnesium alloy along ED exhibits a conventional positive strain rate sensitivity that the dynamic flow stresses increase with increasing strain rate. Texture measurements show that after dynamic tension, the initial weak texture of extruded EW75 magnesium alloy tansforms to a relatively strong <10-10>//ED texture with increasing strain rates. The microstructural analysis demonstrates that dislocation motion are main deformatin mode to accommodate dynamic tensile deformation at high strain rates. In addition, the interactions of dislocation-dislocation and dislocation-second phase lead to the increase of flow stress and strain hardening with increasing strain rate.