Formation of dislocations, precipitates and cavities in He-implanted Mn-Cr austenitic steels

Solution-annealed discs of three Mn-Cr austenitic steels containing different amounts of C and N were uniformly implanted at 310 K with 1000 appm He corresponding to ∝ 0.2 dpa. The samples were subsequently aged at temperature from 923 to 1073 K for various times and, after electropolishing, examined by TEM, EDS and EELS. A study was made of the dislocation loops developing on aging and of the compositional changes in their neighbourhood. The formation and growth of precipitates and He-filled cavities was also investigated together with the elemental segregation to the cavity surfaces. It was found that the microstructural evolution in the three materials can take various forms depending on many parameters. (orig.)