Phenomenon of reversion after ageing in magnesium alloys with gadolinium and samarium

The parameters of reversion after hardening aging of magnesium alloys containing two rare earth metals gadolinium (yttrium group) and samarium (cerium group) were determined at various ratios of their contents. The reversion was observed at short annealing at 250 and 300°С beginning with 5 min after preliminary aging at 200°С up to maximum hardening and consisted of significant softening of the alloys then. Measurements of the electrical resistance indicated that during softening the reverse dissolution of the rare earth metals in magnesium-based solid solution takes place with diminution of the quantity of hardening particles precipitated during aging beforehand. The reverse dissolution of the rare earth metals in solid magnesium increases with increase in the annealing temperature after aging from 250 to 300°С and with increase in the gadolinium to samarium ratio in the alloys.