SOME ASPECTS OF THE MEASUREMENT OF PRECIPITATE SIZE IN THE FIELD-ION MICROSCOPE

The measurement of precipitate size in the field-ion microscope atom probe has been studied by considering the Fe7Mo6 mu-phase precipitate in a Co-bearing C-300 maraging steel. This steel was aged at 510-degrees-C for 2 h in order to produce dense and evenly distributed spheroidal Fe7Mo6 mu-phase precipitates suitable for field-ion microscopy atom probe studies. Precipitate sizes were measured directly from field-ion micrographs, from the maximum size observed in video-recorded field evaporation sequences of images, and by the persistence depth technique. The factors affecting accuracy in each method are discussed and the results are compared with sizes calculated from atom probe composition-depth profiles.