TEM INVESTIGATION OF THE MICROSTRUCTURAL EVOLUTION IN NICKEL DURING MEV HELIUM IMPLANTATION

Microstructural evolution during room temperature (T less than equivalent to 100 degree C) He implantation has been investigated by transmission electron microscopy and compared to previous results on Cu. For c//H//e less than 0. 6 at. %, clustering of irradiation-induced Frenkel defects leads to formation of dislocation loops and stacking fault tetrahedra. Eventually dislocation loops interact to form a dislocation network. For 0. 6 at. % less than equivalent to c//H//e less than equivalent to 3 at. %, the microstructure is dominated by small cavities resulting from precipitation of implanted helium. Two types of vacancy clusters, stacking fault tetrahedra and He-containing cavities, coexist in this concentration range.