Electron microscopic study of dislocations and fission damage in platinum foils

Thin beaten foils of platinum were investigated by means of transmission electron microscopy. Annealed, as well as annealed and subsequently fission-fragment and α-particle irradiated foils were examined. The annealed foils show features which are typical for a face centered cubic metal with a medium high stacking fault energy. Prismatic loops with a 1 2α [110] Burgers vector result from the irradiation; this could be proved by observing their motion. The loops anneal out at the temperature where according to Piercy ¹) vacancies become mobile. Preferential loop formation is noticed at certain boundaries, in particular along coherent twin boundaries. This is considered as evidence that correlated collision chains lead to preferential defect formation at these boundaries by "defocusing" of [110] focussons. It is noticed that for small doses dislocation loops are not distributed at random in the interior of the grains but show a tendency to be aligned. This is interpreted as resulting of loop nucleation along the path of a fission fragment. After quenching, specimens contain both cavities and loops. The damage rate of quenched specimens seems to be larger than that of annealed ones; the loop concentration is less along a denuded zone parallel to boundaries and subboundaries. It is suggested that either the vacancy clusters left by quenching are nucleation sites for loops or that the vacancy clusters defocuss focussons and hence increase the damage. It is shown that the loops left after irradiation are presumably vacancy loops.