Plastic deformation behavior of high purity magnesium was studied in the temperature range between 4.2K and 300K. Tensile tests on polycrystalline samples deformed at 78K exhibit higher yield stress and flow stress than samples deformed at 4.2K. This anomalous behavior was observed consistently in samples of various grain sizes between 13μm to 120μm. To probe the fundamental deformation mechanism responsible for this effect, a series of tensile deformation experiments was conducted on single crystals having different crystallographic tensile axis orientations. Single crystals with five different tensile axis orientations were grown so as to activate principal slip and twinning systems. The anomalous flow stress behavior was observed only in crystals oriented for second order pyramidal slip (c+a slip). Therefore, the activity of this type of slip and its dependence upon the deformation temperature is believed to be responsible for this phenomenon in polycrystalline material. The work hardening behavior, strain rate sensitivity, and texture evolution in both single and polycrystals have been studied in details. In addition, the development of dislocation substructures in deformed samples was investigated by means of electron microscopy studies and electrical resistivity measurements. The results from this research provide a broad range of background data about the plastic deformation behavior of this material and aspects such as: the nature of energy storage, the stability of the deformation substructure, twinning deformation and the limits of plasticity.
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