Investigation of Phase Transformation and Grain Growth in Nanocrystalline Austenitic Stainless Steels Produced by High Energy Mechanical AlloyingWednesday (26.09.2018) 17:15 - 17:30 S1/01 - A3 Part of:
Nanocrystalline stainless steels of different compositions (18/8, 17/12 and 20/25) were produced from elemental powders by high-energy mechanical alloying technique. The phase transformation and grain growth as a function of alloy compositions and annealing temperatures were investigated by room and high temperature x-ray diffraction experiments, transmission electron microscopy and focused ion beam microscopy. The results revealed that stainless steels with low nickel content underwent a deformation-induced martensitic transformation during room temperature mechanical alloying. Deformation induced martensitic transformation with increasing nickel content would not be possible by room temperature milling but was created by high strain rate cryogenic processing, the degree to which was compositional dependent. Post process annealing induced the reverse transformation from martensite- to-austenite the ratio of which was found to be a factor of alloy composition and annealing temperature. The real time in-situ x-ray studies showed that the martensite-to-austenite reverse transformation was completed at high temperatures. Microscopy studies revealed a significant enhancement in the resistance to grain growth for 17/12 steel over other compositions at elevated temperatures as high as 1200 °C. The research reported in this work was supported by TUBITAK under Grant number 114M214. The authors wish to thank TUBITAK for the support.