Effect of Microstructure on the Internal Oxidation of Two-Phase Fe–Y Alloys

Kachur, Stephen J.; Webler, Bryan A.

doi:10.1007/s11085-015-9598-4

Cited by 4 publications

(6 citation statements)

References 20 publications

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“…The work presented here shows that gas phase mass transfer processes affect both internal oxidation kinetics and microstructures. The observation of a transition in rate from Rhines pack samples [18] suggests that the internal oxidation behavior might have been affected by the gas phase in those tests as well. In general, the results show the importance of considering all possible rate-controlling phenomena in studies of internal oxidation, particularly when oxidant pressures are low and fast-path diffusion can occur in the metal.…”

Section: Internal Oxidation Behavior Is An Importantmentioning

confidence: 98%

“…The present authors recently studied effects of microstructure and solute content on in situ oxidation kinetics in Fe-Y alloys containing 1 to 15 wt pct Y [18] oxidized between 873 K and 1073 K (600°C and 800°C) for 2 to 72 hours in an Fe/FeO Rhines pack to establish low oxygen partial pressures. Alloys were two-phase mixtures of a-Fe and Fe 17 Y 2 intermetallic and the volume fraction of the intermetallic varied with yttrium content.…”

Section: Internal Oxidation Behavior Is An Importantmentioning

confidence: 99%

“…These deviations were suggested to be caused by oxide coarsening. [18] In addition, oxidation rates decreased as overall alloy yttrium content increased. This should not have been the case for two-phase alloys because the concentration of yttrium in the oxidizing phase (the Fe 17 Y 2 ) is independent of alloy yttrium content.…”

Section: Internal Oxidation Behavior Is An Importantmentioning

confidence: 99%

“…This explanation was presented in the previous work. [18] To more accurately see how in situ oxidation rates changed over time and with variations in oxygen supply, oxidation experiments in this study were carried out using a Setaram SETSYS Evolution thermogravimetric analysis (TGA) furnace. This allowed continuous weight gain to be measured during oxidation as a function of time so that transitions in kinetic behavior could be observed.…”

Section: Internal Oxidation Behavior Is An Importantmentioning

confidence: 99%

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Influence of Oxygen Supply on Oxide Coarsening During the Internal Oxidation of Two-Phase Fe-Y Alloys

Kachur

Webler

2016

Metallurgical and Materials Transactions E

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Fe-Y binary alloys underwent thermogravimetric analysis while exposed to low oxidant partial pressures using a mixture of 5 pct H 2 -95 pct Ar gas at two flow rates. The alloys experienced in situ internal oxidation of Y-rich intermetallic phases. Kinetics and microstructures were both affected by flowrate. Lower flow rates resulted in coarser oxides and decreased oxidation rates. Results show the possible impacts of rate-controlling processes in the gas phase on internal oxidation with dilute oxidants.

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Section: Internal Oxidation Behavior Is An Importantmentioning

confidence: 98%

Section: Internal Oxidation Behavior Is An Importantmentioning

confidence: 99%

Section: Internal Oxidation Behavior Is An Importantmentioning

confidence: 99%

Section: Internal Oxidation Behavior Is An Importantmentioning

confidence: 99%

See 2 more Smart Citations

Influence of Oxygen Supply on Oxide Coarsening During the Internal Oxidation of Two-Phase Fe-Y Alloys

Kachur

Webler

2016

Metallurgical and Materials Transactions E

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“…The as-cast microstructure consisted of an a-Fe matrix and Fe 17 Y 2 intermetallic, as shown in Figure 1a. Oxides were introduced into the bulk alloy when the material underwent selective internal oxidation, during which the Fe 17 Y 2 intermetallic phase oxidized to Y 2 O 3 particles and pure Fe, leaving the a-Fe matrix unaltered [2].…”

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confidence: 99%

Characterizing the Effect of ECAP on Particle Dispersion and Thermal Stability of Internally Oxidized Fe-Y Alloys

et al. 2018

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Oxide dispersion strengthened (ODS) alloys are desirable for high temperature applications, as dispersed oxide particles within the metal matrix act as barriers to dislocation motion and grain growth at elevated temperatures. Traditional processing routes for ODS alloys are powder metallurgy based, utilizing mechanical alloying by high energy ball milling to mix metal and oxide powders, necessitating compaction techniques such as hot isostatic pressing or hot extrusion to create a dense final product. Recent studies have investigated production of dispersion strengthened alloys without powder metallurgy by introducing a dispersed ceramic phase to a bulk alloy via a physical application process, such as spraying [1], followed by severe plastic deformation to refine grain size. This study proposes an ODS synthesis method of introducing oxides via selective internal oxidation, followed by equal channel angular pressing (ECAP) to refine grain size.In this work, Fe-1.5 wt% Y alloys were studied. The as-cast microstructure consisted of an a-Fe matrix and Fe 17 Y 2 intermetallic, as shown in Figure 1a. Oxides were introduced into the bulk alloy when the material underwent selective internal oxidation, during which the Fe 17 Y 2 intermetallic phase oxidized to Y 2 O 3 particles and pure Fe, leaving the a-Fe matrix unaltered [2].Internal oxidation was followed by ECAP in order to refine the matrix Fe grain size while also dispersing the Y 2 O 3 particles. During ECAP, as illustrated in Figure 1b, strain is introduced as the ingot is pressed through a die at an angle, which for this study was 90°. Because the dimensions of the cross section are the same before and after deformation, the piece can undergo multiple consecutive passes, each introducing additional plastic deformation to the sample. The processing variables studied in this work were the number of ECAP passes and the temperature at which ECAP was performed. In this study, ECAP was performed at room temperature (25°C) and an elevated temperature (350°C), for four ECAP passes and for eight ECAP passes.After ECAP, Fe grains in the matrix were imaged using electron channeling contrast via backscattered electron detection in a FEI Quanta 600 FEG-SEM. Post-ECAP grain size of the Fe matrix was measured using the ASTM E112 linear intercept method [3], finding that increased number of ECAP passes had no significant impact on grain size. A series of thermal stability anneals at 250°C, 400°C, and 1000°C were performed, and Vickers microhardness measurements taken before and after annealing found that the high-temperature ECAP samples maintained similar hardness after 400°C, while room temperature ECAP samples exhibited loss of thermal stability based on an observed significant drop in hardness after 400°C anneals.An automated high-throughput dispersion analysis program was developed to quantify particle dispersion using the quadrat method [4]. Applying the dispersion program to the ECAP samples, it was found that the room temperature ECAP samples had more dispersed particl...

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Fabrication of Oxide‐Dispersion‐Strengthened Ferritic Alloys by Mechanical Alloying Using Pre‐Alloyed Powder

Zhang

Zhao

et al. 2022

steel research int.

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Progress toward controllable nuclear fusion operations largely relies on the high performance of advanced nuclear structural materials. [1][2][3][4][5][6] Attributed to the extremely harsh environments where fusion reactors work, the components suffer from both high level of heat flux and high dose of neutron radiation. Oxide-dispersion-strengthened (ODS) steel is one of the most promising candidate structural materials for the next-generation fusion reactors due to its excellent resistance to high-temperature creep, corrosion, and neutron radiation. [7][8][9][10][11][12] ODS steels are mainly based on the reduced activated alloys such as Fe-Cr-W system. These alloys can be divided as reduced activated ferritic martensitic (RAFM) steels with a lower Cr (9-12 wt%) content and reduced activated ferritic (RAF) ones with a higher Cr (>12 wt%) content. Unlike RAFM steels, the RAF steels do not experience a γ-α transformation at elevated temperatures. Therefore, they can be operated at a higher temperature and have a better resistance to radiation swelling. [13][14][15] ODS steels possess a huge number of nano-oxides that are thermally stabilized in the matrix. These nanoparticles can not only hinder the movement of dislocations, but also absorb the point defects induced by irradiation, enhancing the pore expansion resistance and preventing void swelling of the materials under neutron irradiation. [16][17][18][19][20][21] For these reasons, a higher number density, a finer size, and a better distribution of the oxides are always pursued.Mechanical alloying (MA) is one of the most widely used methods to prepare ODS steels, where Y 2 O 3 powder is often added to the steel powder for long-term high-energy ball-milling. During MA, a large amount of lattice defects (e.g., vacancies and dislocations), along with the supersaturated dissolved Y and O atoms that are decomposed from the Y 2 O 3 powder, can be gradually restored in the powders. Then, powder metallurgy is conducted to this non-equilibrious MA powders to build the components with proper sizes and shapes. [22] In this step, one of the following densification strategies, that is, hot extrusion (HE), hot isostatic pressing (HIP), or spark plasma sintering (SPS), is usually carried out. [23][24][25] Assisted by the subsequent heat treatment, a huge number of Y 2 O 3 nanoparticles win the chance to simultaneously precipitate from the supersaturated matrix. In the earlier procedures, MA is definitely a timeconsuming stage. It takes an extremely long period, usually longer than 50 h, for the complete decomposition and dissolution of Y 2 O 3 through ball-milling since it has the highest bonding energy among most of the common oxides. [24][25][26] If MA process can be accelerated by a faster decomposition of the oxide

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Effect of Microstructure on the Internal Oxidation of Two-Phase Fe–Y Alloys

Cited by 4 publications

References 20 publications

Influence of Oxygen Supply on Oxide Coarsening During the Internal Oxidation of Two-Phase Fe-Y Alloys

Influence of Oxygen Supply on Oxide Coarsening During the Internal Oxidation of Two-Phase Fe-Y Alloys

Characterizing the Effect of ECAP on Particle Dispersion and Thermal Stability of Internally Oxidized Fe-Y Alloys

Fabrication of Oxide‐Dispersion‐Strengthened Ferritic Alloys by Mechanical Alloying Using Pre‐Alloyed Powder

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