Radiation Effects on Molybdenum Alloys Bombarded by Electrons in a High-Voltage Electron Microscope

Abstract

The objective of this study is to clarify the dislocation loop formation and the subsequent void swelling and also to reconsider the use of the high-voltage electron microscope (HVEM) as simulation study for neutron or other particle irradiation. In situ observation of damage processes in molybdenum carbon alloys was performed by HVEM in the temperature range between 300 and 1300 K with the dose level up to 10 displacements per atom (dpa). Dislocation loop density was observed as the function of irradiation temperature. Below 500 K the density was interpreted to mean that the nuclei for interstitial clusters are di-interstitials. Above 500 K, however the instability of the interstitial clusters was observed. The dislocation loop formation and the succeeding dislocation behavior were observed above 1000 K and four stages were observed. Void swelling was observed after the dislocation density reached steady state. The effect of the surface on dislocation behavior was found to be very important. The void swelling was proportional to the third power of irradiation time, similar to other irradiation data.