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Microstructural studies of oxide dispersion strengthened austenitic steels
K. Suresh, M. Nagini, R. Vijay, M. Ramakrishna, R.C. Gundakaram, A.V. Reddy,
Published in Elsevier Ltd
Volume: 110
Pages: 519 - 525
Oxide dispersion strengthened (ODS) austenitic steel (Fe-16.8Cr-22Ni-2W-2.4Mo-1.5Mn-0.62Si-0.15La-0.2Ti + 0.35Y2O3, wt%) was prepared by mechanical alloying and consolidated by hot extrusion followed by solutionization at 1150 °C for 1 h. The composition of this steel is designed to suppress the formation of deleterious delta (δ-) ferrite and sigma (σ-) FeCr phases, which reduces the life the materials. Various microscopic, spectroscopic and diffraction techniques were employed to study the hierarchical microstructural features of this alloy. X-ray diffraction studies confirm the austenitic phase and no traces of δ-ferrite phase were observed in as-extruded and solutionized conditions. The solutionized austenitic ODS steel exhibited ultra-fine grain structure having mean sizes of 280 ± 5 and 440 ± 9 nm in transverse and longitudinal sections of the bar, respectively. Evenly dispersed high density of Y-Ti-O nano-oxides with a mean size of 9 nm was achieved along with low fractions of TiC and La rich Y2Si2O7. The crystal structure of Y-Ti-O nano-oxides was determined by combining HR-TEM and FFT techniques and was found to be pyrochlore Y2Ti2O7. These dispersoids and ultra-fine grain structure of austenitic steel contribute to an enhanced hardness of 346 ± 25 HV. © 2016 Elsevier Ltd
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JournalData powered by TypesetMaterials and Design
PublisherData powered by TypesetElsevier Ltd