Observation of Defect Clusters of Columbium and Columbium Alloys In Situ Irradiated Under a High-Voltage Electron Microscope

Abstract

The nucleation and growth mechanisms of self-interstitial dislocation loops in columbium, columbium-oxygen, columbium-zirconium, and columbium-molybdenum, were studied by the electron irradiation and in situ observation in the temperature range from 10 K to 500 K, using a high-voltage electron microscope. The loop density increased in proportion to the square root of interstitial oxygen concentration. The density first decreased and then increased with the increase in zirconium and molybdenum concentrations. The logarithm of loop density was proportional to the reciprocal irradiation temperature. The growth rate of loops was suppressed by interstitial oxygen atoms; it was enhanced and then suppressed as the concentrations of substitutional zirconium and molybdenum atoms increased. The nucleation and growth mechanisms of self-interstitial loops were discussed from the viewpoint of the trapping effect of self-interstitials and vacancies by alloying atoms. The scavenging effect by zirconium and molybdenum atoms was also discussed.