Effect of temperature change on microstructural evolution of vanadium alloys under neutron irradiation in JMTR

Recently, it has been pointed out that the effect of varying temperature on microstructural evolution in materials under neutron irradiation can be ve ry complicated. In this paper, evolution of microstructure in vanadium allo ys in each step of temperature changes is closely examined in order to anal yze the effects after several temperature cycles. Neutron irradiation was p erformed in JMTR with an upward temperature change. TEM observation, micro- Vickers hardness test and positron annihilation lifetime spectroscopy have been carried out on vanadium alloys. During the irradiation at 220 degrees C, a lot of small defects have nucleated. They grew up after the upward tem perature step to 420 degrees C. On the other hand, microstructure remained essentially the same in the irradiation at 340/530 degrees C temperature co mbination. Vanadium alloys containing titanium show different tendencies; u nlike other alloys, a number of radiation induced precipitates were found b y TEM in these alloys. (C) 1999 Published by Elsevier Science B.V. All righ ts reserved.