MICROSTRUCTURE AND MECHANICAL PROPERTIES OF OXIDE DISPERSION STRENGTHENED HIGH-ENTROPY ALLOYS CoCrFeMnNi AND CrFe2MnNi

High-entropy alloys (HEAs) CoCrFeMnNi and CrFe2MnNi, dispersion-strengthened by pre-synthesized nanooxides composition of 80%Y2O3+20%ZrO2 (mol.%) were obtained by mechanical alloying followed by compaction and sintering. Average grain size of the oxide dispersion-strengthened (ODS) alloys was about 2 μm. Oxide precipitates in alloys are characterized by the presence of small particles with an average size of about 10 nm and a density of ≈ 1021 m-3, as well as small amount of larger particles sizes of 50…150 nm. The qualitative composition of particles of different sizes has been established. Mechanical properties of HEAs were studied at different temperatures. It is shown that strengthening of the studied alloys by nanooxide particles leads to a significant increase in strength characteristics.

High-Temperature Oxidation Properties and Microstructural Evolution of Nanostructure Fe-Cr-Al ODS Alloys

The oxidation behavior and microstructural evolution of the nanostructure of Fe-Cr-Al oxide dispersion strengthened (ODS) alloys prepared by spark plasma sintering were investigated by high-temperature oxidation experiments in air at 1200 °C for 100 h. The formation of Al2O3 scale was observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) line scans. The oxidation rate of Fe-Cr-Al ODS alloys is lower than that of conventional Fe-Cr-Al alloys, and the oxide layer formed on the Fe-Cr-Al alloy appeared loose and cracked, whereas the oxide layer formed on the Fe-Cr-Al ODS alloys was adherent and flat. This is due to the high density of dispersed nano-oxides hindering the diffusion of Al element and the formation of vacancies caused by them. In addition, the nano-oxides could also adhere to the oxide layer. Besides, the microstructure of the Fe-Cr-Al ODS alloy had excellent stability during high-temperature oxidation.

Influence of Hot Consolidation Conditions and Cr-Alloying on Microstructure and Creep in New-Generation ODS Alloy at 1100 °C

The coarse-grained new-generation Fe-Al-Y2O3-based oxide dispersion strengthened (ODS) alloys contain 5 vol.% homogeneously dispersed yttria nano-precipitates and exhibit very promising creep and oxidation resistance above 1000 °C. The alloy is prepared by the consolidation of mechanically alloyed powders via hot rolling followed by secondary recrystallization. The paper presents a systematic study of influence of rolling temperature on final microstructure and creep at 1100 °C for two grades (Fe-10Al-4Y2O3 and Fe-9Al-14Cr-4Y2O3 in wt%) of new-generation ODS alloys. The hot rolling temperatures exhibit a rather wide processing window and the influence of Cr-alloying on creep properties is evaluated as only slightly positive.

Vacuum Hot Pressing of Oxide Dispersion Strengthened Ferritic Stainless Steels: Effect of Al Addition on the Microstructure and Properties

The present article investigates the fabrication of oxide dispersion strengthened (ODS) ferritic stainless steel (FSS). Three different ODS alloys with three different Al contents were fabricated, where the presence of Al-based oxides play a crucial role in determining the size of the oxide particles. Due to Ostwald ripening, the samples with Al show coarser oxide particles compared to the alloy without Al, which hampers the density of the fabricated samples and, hence, have reduced hardness levels. The present results suggest that the composition of the oxide present in ODS plays a crucial role in determining the properties of these samples.

Effect of Hot Rolling on the Microstructure and Properties of Nanostructured 15Cr ODS Alloys with Al and Zr Addition

Oxide dispersion strengthened (ODS) alloys with Al and Zr addition have excellent radiation tolerance, high-temperature strength, and corrosion resistance. The 15Cr-Al-Zr-ODS alloys are processed by mechanical alloying (MA), hot isostatic pressing (HIP), subsequent hot rolling to large strains of 70%, and further annealing. The effect of hot rolling on the microstructure, and the properties of nanostructured 15Cr ODS alloys with Al and Zr addition, were investigated. The microstructure after hot rolling and annealing showed obvious anisotropy. The cubic texture (φ1 = 0°, Φ = 0°, φ2 = 0°) {0 0 1} <1 0 0> and brass-R texture (φ1 = 0°, Φ = 55°, φ2 = 45°) {1 1 1} <1 1 0> were observed. The similar size distribution of precipitates was obtained for the comparison of the hot rolling samples with the hot isostatic pressed samples, which can be attributed to excellent thermal stability. After hot rolling, the alloy showed higher yield strength but did not lose too much plasticity.