An internal variable approach to creep behavior of pure magnesium poly and single crystals

Abstract

A new interpretation for the creep behavior of pure magnesium single crystals as well as poly crystals with 99.94 mass % purity has been made by using an internal variable approach. A series of load relaxation tests and creep tests for magnesium single and poly crystals were performed at elevated temperature. The single crystals used in this study were grown from the melt using a modified Bridgman technique. The creep behavior has been well described by the internal variable theory based on dislocation dynamics, consisting of two deformation modes; dislocation glide and dislocation creep deformation modes. The flow curves obtained from the load relaxation tests at elevated temperature could be resolved into a dislocation glide and a creep component effectively by the internal variable theory. The dislocation creep component above 523 K for single crystal magnesium shifted toward the faster strain rate regime with increasing temperature. This could be due to activation of the cross-slip of dislocations from basal to prismatic planes above 523 K.