ELECTRON-IRRADIATION DAMAGE IN TITANIUM

Point defects created by electron irradiation can cluster into prismatic dislocation loops and voids during in situ bombardment in a high voltage electron microscope (HVEM). The authors have observed the development of such loops in Ti. Disc specimens of vacuum annealed 99. 5% pure Ti were electrothinned in a perchloric-butylcellosolvemethanol solution at 5 degree C and were irradiated in a Hitachi HVEM operating at 635 kV. Large grains of uniform thickness (approximately 0. 5 mu m or thicker) were chosen for irradiation at two different temperatures 350 degree C and 450 degree C. No visible displacement damage was detected at 350 degree C in several areas irradiated to elapsed times ranging from 13 min up to 1 hr. At 450 degree C, in limited cases of grain orientation, defect clusters in the form of prismatic dislocation loops were observed to grow.