HYDROGEN TRAPPING IN HELIUM DAMAGED METALS - A THEORETICAL APPROACH

A model which explains the trapping of hydrogen around or near helium bubbles is presented. According to this model, hydrogen atoms are attracted toward the bubbles due to positive stresses created by the very high pressure (350 kbar) existing inside the bubbles. The extreme trapping energy of hydrogen atoms around helium bubbles has been theoretically calculated and found to be 0.71 eV atom-1. It is shown that most of the hydrogen atoms are trapped in a very small volume located very close to the bubble surface. The total hydrogen quantity was found to be in the range of 45 76 atoms per bubble for a wide range of hydrogen atom concentration, C infinity. The good agreement between the theoretical results and data based on many experimental measurements reinforces the assumptions underlying the very basis of the suggested mechanism. The model proposed in this study can lead to better understanding of failure mechanisms.