Nanostructure of Oxide Dispersion-Strengthened Steel Mechanically Alloyed with Intermetallic Fe3Y

Abstract

In this work, the nanostructure of oxide dispersion-strengthened steel 13.5Cr–Fe₃Y ODS, obtained by mechanical alloying of oxidized matrix steel powder and Fe₃Y intermetallic powder. In addition to the initial state, the effect of thermal aging on the nanostructure of this steel at 650°C for 500 and 1000 h was investigated. In the studied states of 13.5Cr–Fe₃Y ODS steel, transmission electron microscopy (TEM) has detected nanoscale oxides (~10–12 nm) with a number density of ~4–7 × 10²¹ m^–3, pores (~3.0–3.6 nm and ~2–4 × 10²² m^–3), as well as the dislocations ~2 × 10¹⁴ m^–2. According to the energy-dispersive X-ray spectroscopy analysis, oxide particles are mainly enriched in Y and O, and the detected pores contain up to 3 at. % Ar. Atom probe tomography (APT) revealed the presence of clusters (~3–5 nm and ~8–30 × 10²² m^–3). The detected clusters also contain Ar within 0.1 at. %. Comparison of the data on the initial state and states after thermal aging revealed an increase in the number density of oxides and a decrease in their size with an increase in the thermal aging time, while the volume of the oxide phase at 1000 h remains the same relative to the initial state within the limits of error. Comparison of APT data showed an increase in the volume of clusters during aging up to 500 h and a decrease in the volume at 1000 h. An increase in the number of oxides during thermal aging up to 1000 h correlates with a decrease in the volume of clusters in the same state. There is a significant (~2 times) decrease in pore volume during thermal aging. The density of dislocations increases to ~5 × 10¹⁴ m^–2 when reaching 1000 h of aging.