DETERMINATION OF THE MICROSTRUCTURE AND ALLOY ELEMENT DISTRIBUTION IN EXPERIMENTAL DUPLEX STAINLESS-STEELS

An investigation was carried out on the microstructure and distribution of alloy elements in a series of experimental duplex stainless steels containing up to 35% chromium. It was found that the proportion of austenite and ferrite present could be accurately measured using either metallographic image analysis or x-ray diffraction. However, potentiostatic etching techniques were required for the metallographic image analysis. A comparison of the two methods showed equivalent results, except when the orientation of the individual grains departed significantly from random. The chemical compositions of the austenite and ferrite phases were determined using a scanning electron microscope and an electron microprobe. Significant partitioning of the alloying elements was found to occur. The application of a mass balance calculation was used to determine which of the four possible combinations of techniques would provide the most accurate characterization of the alloys.