Substantial Improvement of High Temperature Strength of New-Generation Nano-Oxide-Strengthened Alloys by Addition of Metallic Yttrium

Abstract

Oxide-dispersion-strengthened (ODS) Fe-Al-Y2O3-based alloys (denoted as FeAlOY) containing 5 vol. % of nano-oxides have a potential to become top oxidation and creep-resistant alloys for applications at temperatures of 1100–1300 °C. Oxide dispersoids cause nearly perfect strengthening of grains; thus, grain boundaries with limited cohesive strength become the weak link in FeAlOY in this temperature range. One of the possibilities for significantly improving the strength of FeAlOY is alloying with appropriate elements and increasing the cohesive strength of grain boundaries. Nearly 20 metallic elements have been tested with the aim to increase cohesive strength in the frame of preliminary tests. A positive influence is revealed for Al, Cr, and Y, whereby the influence of Y is enormous (addition of 1% of metallic Y increases strength by a factor of 2), as it is presented in this paper.

Coarsening Kinetics of Y2O3 Dispersoid in New Grade of Fe-Al-Cr-Based ODS Alloy

“…That is why a certain portion of coarsening can still keep a sufficient hardness of the grains without any change in creep properties. A detailed discussion concerning this topic can be found in [31]. The influence of the oxide coarsening on the creep and tensile test properties at 1100-1300 • C will be a topic of the follow-up paper.…”

The Optimization of Mechanical Alloying Conditions of Powder for the Preparation of a Fe-10Al-4Cr-4Y2O3 ODS Nanocomposite

“…To provoke precipitation of only the most stable pure Y 2 O 3 nanodispersoid, O introduced into the system by oxidized powder surfaces is compensated by the addition of metallic Y granulates (about 1%). The addition leads also to a coarser grain microstructure after secondary recrystallization and a significant increase in the high-temperature strength of the FeAlOY [42]. The high Al content not only significantly improves the oxidation resistance but, surprisingly, also improves the high-temperature strength of the FeAlOY.…”

“…The authors have dealt with the development of the FeAlOY since 2014 [31,[36][37][38][41][42][43]45,46]. The recent efforts include optimization of hot consolidation, secondary recrystallization, and chemical composition with respect to resultant microstructure and high-temperature mechanical properties.…”

“…The creep and oxidation-resistant Fe-10Al-4Cr-4Y 2 O 3 (wt.% are used in the whole paper) ODS nanocomposite, denoted as the FeAlOY, has already demonstrated its promising potential for mechanically loaded long-term applications in the temperature range of 1100-1300 • C [31,36,38,41,42]. The FeAlOY is strengthened by 5 vol.% of nanodispersion of pure Y 2 O 3 (the difference between 5 vol.% and 4 wt.% is given by the difference in densities of the matrix 6.5 g/cm 3 and of Y 2 O 3 5.0 g/cm 3 ), being the most resistant phase against coarsening [41,43], and has an appreciable resistance against oxidation up to 1400 • C [44].…”

Phase Equilibria of the Fe–Cr–Er Ternary System in the Range 973–1273 K

“…Oxide dispersion-strengthened (ODS) steel, which developed from martensitic and ferritic steels, is the most promising candidate for nuclear reaction cladding [ 1 ]. ODS steel is strengthened by dispersing oxide particles, which strongly impede dislocation motion and thereby increase the onset stress of plastic deformation and creep resistance [ 2 , 3 ].…”