A NEW OBSERVATION METHOD OF A PHASE IN AU STENITIC STAINLESS-STEELS

In order to establish an appropriate process for observation of distri bution of sigma-phase particles in austenitic stainless steels, which enables observation of a large numbers of specimens in a short time, e xtraction replica methods combined with image-processing technique wer e explored. Obtained results are as follows: (I) For sigma-phase in SU S316H steel, any of the following three extraction method works satisf actorily: (1) electrolytic etching by 10% acetylacetone-1%HCl-metanol followed by extraction by the same electrolyte; (2) etching by 10%Br-2 -ethanol solution followed by extraction by Villella's solution. (3) etching by Villella's solution followed by extraction by the same solu tion. (II) For sigma-phase in SUS304H and SUS321H steels, the third me thod above is suitable. (III) For exclusive observation of the a-phase particles from other coexisting M(23)C(6), TiC and Laves phase partic les, image-processing is useful.