Steady-State Creep and Strain Transients for Stress-Dip Tests in Polycrystalline Magnesium at 300 °C

High purity (99.99%) polycrystalline magnesium is creep tested in air at 300 °C and the stress-dip test used to determine the effective (σe) and internal (σi) stresses. The stress exponent of steady state creep, and the shape of the primary creep curve, indicate recovery (climb) creep to be rate controlling. There is an instantaneous non-elastic strain for all levels of stress decrement in the stress-dip tests. The absence of incubation periods of zero creep rate in the stress-dip tests, except for one particular value of the stress drop, favour the applicability of glide-recovery rather than straight recovery mechanisms for the high-temperature creep of magnesium. The internal stress varies with the applied stress, σ, increasing with increasing σ. σi/σ ratios of about 0.9 agree with previous data for pure metals.