Papers by Keyword: Positron Annihilation Techniques

Abstract: Positron annihilation lifetime (PAL) is one of the most important nuclear techniques used in material science. Electrical measurements are also used in material science. Samples of 25 % deformation have been used for these studies. Both positron annihilation lifetime and electrical measurements were used to determined the activation energy of migration the dislocation in 7075 alloy. The isothermal annealing measurements were performed at 643, 663, 683 and 703 K. The activation energy of migration the dislocation are obtained as 1.35 ± 0.16 eV and 1.25 ± 0.05 eV for positron annihilation lifetime and electrical techniques respectively.

Abstract: Zr-based bulk glassy (BG) alloys show high tensile strength and a high Charpy impact value. In this study, the free volume changes for the hypoeutectic Zr60Cu30Al10 BG alloy during isothermal annealing below glass transition temperature (Tg) have been investigated by positron annihilation lifetime and coincidence Doppler broadening (CDB) measurements. The positron lifetime of hypoeutectic and eutectic BG alloys is almost the same, although the atomic volume ratio, estimated by the density for the eutectic BG alloy is different from that for the hypoeutectic BG alloy. The CDB spectra show a marked difference between eutectic and hypoeutectic BG alloys; that is, the spectrum of the hypoeutectic BG alloy is closes to that of Zr metal than that of the eutectic BG alloy. This result exhibits that the elemental fraction of Zr atoms around free volume in hypoeutectic BG alloy is greater than that in eutectic BG alloy. The CDB ratio profiles for the hypoeutectic BG alloy during annealing shows no appreciable change. The same trend was observed in the eutectic BG alloy.