Dynamic behavior of nano-voids in magnesium under hydrostatic tensile stress

We investigate the mechanisms responsible for nano-void growth in single crystal magnesium under dynamic hydrostatic tensile stress. A key conclusion derived from our study is that there is no secondary strain hardening near the nano-void. This behavior, which is in remarkable contrast to face-centered cubic and body-centered cubic materials, greatly limits the peak stress and explains the relatively lower spall strength of magnesium. The lack of secondary strain hardening is due to the fact that pyramidal dislocations do not interact with basal or prismatic dislocations. Our analysis also shows that for loads applied at moderate strain rates ((epsilon) over dot <= 10(6) s(-1)) the peak stress, dislocation velocity and temperature distribution converge asymptotically. However at very high strain rates ((epsilon) over dot >= 10(8) s(-1)), there is a sharp transition in these quantities.