Formation mechanism of clustered small loops (rafts) in fission-neutron irradiated Mo at high temperatures

摘要

Clustered small loops were observed, by transmission electron miroscope, in fission-neutron irradiated molybdenum at high temperatures and referred to as a raft. The groups of small dislocation loops (rafts) were observed at one side of the dislocations or inside of the large interstitial loops. The small loops in a raft aligned in rows. Burgers vector of the small loops was the same as that of the dislocation or large loop. The nature of small loops in the rafts was a vacancy type. It was also observed that the dislocation dipoles were just chopping into small loops. Therefore, formation mechanism of the rafts is as follows: Interstitial atoms aggregate and form loops, which grow to large convoluted loops. The dislocation dipoles on the convoluted loops are chopped off to form the rows of small loops. By this mechanism, the small loops in the rafts have to be opposite type in nature against the large interstitial loops.