ffects of time and strain on material strength. With this objective, we performed a careful
comparative measurement of the free-surface velocity of shock loaded aluminium AD1 and
magnesium alloy Ma2 samples of various thicknesses in the range 0.2 mm to 5 mm. We
observed the expected decay in the elastic precursor state with increasing sample thickness
for both aluminium and magnesium alloy. However, we also observed a small change in the
magnitude of hysteresis in the elastic-plastic compression-unloading cycle; where qualitatively
the peak free-surface velocity also increased with increasing specimen thickness. Interestingly,
the observed change in hysteresis as function of specimen thickness for the Ma2 alloy was
relatively smaller than the AD1, in contrast with the larger change in precursor magnitude
observed for the magnesium. We propose that softening due to multiplication of dislocations is
relatively large in Ma2 and results in a smaller hysteresis in the elastic-plastic cycle.