Microstructural observation and tensile properties of ODS-304 austenitic steel

ODS-304 austenitic steel (pre-alloyed austenitic steel powders +0.35 wt% Y2O3+0.5 wt% Ti) was fabricated by the process of mechanical alloying and hot isostatic pressing. The milled powders were characterized by XRD and SEM. New peaks of YO1.401 appeared after milling of 5 h, which indicated that Y2O3 decomposed and dissolved into the matrix during MA. A bimodal distribution of grains was found in the as-HIPed specimen by TEM. It was found that fine oxide particles enriched in Y–Ti–O were dispersed in the small grains, while there were almost no dispersoids inside the large grains. Plastic deformations, including forging and hot rolling, were subjected to the as-HIPed specimens. Tensile properties were measured at 23 and 700 °C. At 23 °C, the UTS and elongation of the as-HIPed specimen reached 940 MPa and 24.5% respectively. Specimens showed much higher ductility after plastic deformations while there was just slight decrease of tensile strength at the same time.