Positron lifetimes in heat treated and plastically deformed iron

The effect of heat treatment and deformation on positron annihilation in pure iron and steel SAE-1006 using the method of lifetime measurement are briefly reported. The positron meanlife remains practically unchanged for iron 99.95 % quenched at temperatures from 650 to 1150 0C. For steel SAE-1006, the positron lifetime is at a minimum near the eutectoid temperature. The positron lifetime in annealed iron of 99.95 %, 0.202 ns, is slightly higher than that in a purer iron of 99.99 %, whereas it is definitely lower in SAE-1006 than that in purer iron. The results of the two methods used to test the effect of deformation (hammering using a hand hammer, and pressing under a hydraulic press) are quite different. This is explained following the trapping theory. It seems that hammering creates void types of defects, which increase the positron lifetime. Hydraulic pressing is a process without shock which may create a different type of defect which reduces the positron lifetime