Microstructure Evolution of Mechanically Alloyed ODS Ferritic Steels during Hot Extrusion

2011 ◽  
Vol 172-174 ◽  
pp. 721-726 ◽  
Author(s):  
Mathieu Couvrat ◽  
Laurent Chaffron ◽  
Daniel Nunes ◽  
Patrick Bonnaillie ◽  
Marie Hélène Mathon ◽  
...  
Keyword(s):  
Dynamic Recovery ◽  
Hot Extrusion ◽  
Oxide Dispersion Strengthened ◽  
Mechanically Alloyed ◽  
Material Microstructure ◽  
Consolidation Process ◽  
Ods Steel ◽  
Complex Process ◽  
Steel Bars ◽  
Nano Cluster

Direct hot extrusion of powder is the standard consolidation process to transform mechanically alloyed Oxide Dispersion Strengthened (ODS) steels into fully dense bars. It is a complex process including several steps. In this study, ODS steel bars were extruded and the material microstructure was characterized by TEM observations associated to SANS after each step. It was shown that the nano-cluster nucleation occurs during the powder pre-heating before hot-extrusion. During extrusion, the ferritic matrix undergoes a dynamic recovery but no further change of the nano-cluster distribution is observed.

Effect of Minor Alloying Element on Dispersing Nano-particles in ODS Steel

2006 ◽  
Vol 981 ◽  
Author(s):  
Y. Uchidi ◽  
S. Ohnuki ◽  
N. Hashimoto ◽  
T. Suda ◽  
T. Nagai ◽  
...  
Keyword(s):  
Hot Extrusion ◽  
Complex Oxides ◽  
Oxide Dispersion Strengthened ◽  
Ferrite Matrix ◽  
Nano Particles ◽  
High Temperature Strength ◽  
Ods Steel ◽  
Ma Process ◽  
Materials Used ◽  
Ti Addition

AbstractFrom the irradiation resistance and high-temperature strength, oxide dispersion strengthened (ODS) ferritic steels are candidate materials for advanced and fusion reactors. For the development of advanced steels the key issue is to homogenize nano-particles into matrix. Recent studies have indicated that Ti addition can homogenize Y-Ti complex particles into ferrite matrix, but the reason of the effect of additional elements has not been clarified. In this model study, we focus on the effect of additional elements, such as IV and V families and other oxide formers, which can control potentially the distribution of the oxide particles. The materials used in this study were based on Fe-9Cr-Y2O3 alloys which were mechanical alloyed (MA) from the powder of Fe, Cr and Y2O3, which was added systematically with the element of Ti, Zr, Ta, V, Nb, Hf, Al, Si and others. Usually ODS fabrication process is required for hot extrusion, but we annealed up to 1150 C for simplify the microstructure. To evaluate the distribution of ODS particles; we used TEM equipped with EDS after electro-polishing or FIB techniques. (1) In the case of Si or Al addition, oxides were disappeared after MA process, which means Y2O3 and other elements should be in solution at non-equilibrium condition. Two types of oxides of Y2O3 and Al2O3 or SiO2 developed after the annealing at 850 C, but only complex oxides were developed after the annealing at 1150 C. This result suggests that the oxide formation is independent process for Y and Si or Al. (2) In the case of Ti addition, oxides also were disappeared after MA process, but developed after annealing at 1150 C. This means that Ti can stabilize complex oxides of Y and Ti, and enhance the fine distribution of the oxides comparing with simple Fe-9Cr-Y2O3 alloy.

Mechanical and Microstructural Properties of Al-Added ODS Ferritic Steel

2012 ◽  
Vol 567 ◽  
pp. 49-53 ◽  
Author(s):  
Jae Hoon Lee
Keyword(s):  
Hot Extrusion ◽  
Oxide Dispersion Strengthened ◽  
Tensile Tests ◽  
Ods Steel ◽  
Dispersed Particles ◽  
Oxide Particles ◽  
Ods Steels ◽  
Ductile To Brittle Transition ◽  
The Difference ◽  
Mechanical And Microstructural Properties

18%Cr-oxide dispersion strengthened (ODS) ferritic steels with and without 5%Al have been produced by mechanical alloying and hot-extrusion. The microstructure of the ODS steels has been characterized by means of electron microscopy (SEM, TEM), showing that in the Al-added ODS steel, the semi-coherent and coherent oxide particles are about 75% and 10%, respectively. It was found that the coherency of oxide particles depends on the size of dispersed particles. Tensile tests performed between room temperature and 973 K denote that the ultimate tensile strength of Al-free ODS steel is higher than that of Al-added one. The ductility values of both materials are sufficiently high. Impact tests reveal that the ductile-to-brittle transition temperature of Al-free ODS steel are higher than that of Al-added ODS steel; however, the upper shelf energy of 18%Cr-ODS steel is substantially smaller in comparison to the Al-added one. It is considered that the difference in mechanical properties between Al-free and Al-added ODS steels is caused by the smaller, stable titania + yttria complex oxides dispersed in the Al-free ODS steel.

scholarly journals CORROSION RESISTANCE OF MECHANICALLY ALLOYED 14%Cr ODS FERRITIC STEEL

2013 ◽  
Vol 7 (1) ◽  
pp. 38-41 ◽  
Author(s):  
Zbigniew Oksiuta ◽  
Ewa Och
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Austenitic Stainless Steel ◽  
Ferritic Steel ◽  
Oxide Dispersion Strengthened ◽  
Localized Corrosion ◽  
Oxide Dispersion ◽  
Steel Matrix ◽  
Mechanically Alloyed ◽  
Ods Steel

Abstract The paper presents results of the corrosion resistance of mechanically alloyed oxide dispersion strengthened 14% Cr ferritic stainless. The oxide dispersion strengthened steel was prepared by means of the powder metallurgy route that consists of mechanical alloying of a pre-alloyed argon atomized steel powder (Fe-14Cr-2W-0.3Ti) with 0.3 Y2O3 (wt%), followed by HIPping at 1150°C and annealing at 850°C for 1 h. The density of ODS ferritic steel after consolidation was about 99.0% of theoretical alloy density. The potentiodynamic corrosion tests were performed for 1h and 24 h of material exposure in a physiological saline solution. For comparison the 316 LV austenitic stainless steel was also examined. The obtained results revealed that both materials were in a passive stage, however the lower current corrosion density was measured for 316 LV steel. On the contrary, the austenitic stainless steel exhibited unstable chemical processes at the passive region. On the surface of both materials localized pitting corrosion was observed with different morphology of the cavities. A broken oxide scale with poor adhesion to the ferritic steel matrix with large number of density of localized corrosion attack was observed on the surface of the ODS steel.

scholarly journals EFFECT OF ULTRASONIC TREATMENT ON THE CONSOLIDATION OF ODS STEEL FeCrY2O3 PROCESSING WITH CAPSULATED SINTERING PROCESS.

2020 ◽  
Vol 21 (4) ◽  
pp. 151
Author(s):  
Marzuki Silalahi ◽  
Bernardus Bandriyana ◽  
Harum Andriadi Bayu ◽  
Bambang Sugeng ◽  
Rohmad Salam
Keyword(s):  
Ultrasonic Treatment ◽  
Oxide Dispersion Strengthened ◽  
Nuclear Material ◽  
Raw Material ◽  
Main Process ◽  
Powder Metallurgy Method ◽  
Sintering Process ◽  
Consolidation Process ◽  
X Ray ◽  
Ods Steel

EFFECT OF ULTRASONIC TREATMENT ON THE CONSOLIDATION OF ODS STEEL FeCrY2O3 PROCESSING WITH CAPSULATED SINTERING PROCESS. A new method on the synthesis of ODS (Oxide Dispersion Strengthened) steel for advanced nuclear material was performed by ultrasonic treatment to improve the consolidation process. The raw material of Fe, Cr and Y2O3powder with the composition of Fe-15 wt% Cr, 0.5 wt% and Ytria (Y2O3)  as disperzoid were  processed by the powder metallurgy method with the main process of pre-alloying, iso-compaction and sintering process. The pre-alloying process was carried out by mixing the alloying elements using ultrasonically treatment at frquency of 20 kHz with variation of  40, 50 and 60 % amplitude. Iso-compaction process was done using the load of  800 psi to obtain a pellet-shaped sample, then continued by the sintering process for consolidation. The sintering process was done in two stages, 1-step sintering and 2-steps sintering, using the heating furnace by putting the sample in a quartz capsule to prevent oxidation attack. Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS), X-ray Diffraction (XRD), and Micro-hardness tests were carried out to analyze the microstructure and phase formation in relation to the consolidation process. The highest hardness occurred in the addition of treatment with an amplitude of 60% which produces a micro structure with the most fine grain. For 1-step sintering process, the highest hardness of 134.51 VHN obtained at 40 % amplitude. The hardness of the alloy depends on the size of the grain boundary associated with the difficulty of the dislocation movement.

Manufacturing of ODS RAFM Steel: Mechanical and Microstructural Characterization

2016 ◽  
Vol 879 ◽  
pp. 1639-1644
Author(s):  
Claudio Testani ◽  
Paolo Emilio di Nunzio ◽  
Ilaria Salvatori
Keyword(s):  
Hot Extrusion ◽  
Microstructural Characterization ◽  
Oxide Dispersion Strengthened ◽  
Processing Parameters ◽  
Ultimate Tensile Stress ◽  
Irradiation Damage ◽  
Ods Steel ◽  
Structural Applications ◽  
Fusion Applications ◽  
Rafm Steel

Ferritic ODS 14Cr steels reinforced by means of Yttrium oxide nanoclusters represent one of the options for future structural applications in nuclear Generation IV reactors. Due to their high tensile properties and resistance to irradiation damage, Oxide Dispersion Strengthened Steels (ODS-S) have been suggested for nuclear fusion applications. The present paper describes the experimental procedure of mechanical alloying, canning and hot extrusion adopted to produce ODS rods. The effect of variations in the processing parameters are also discussed. Hot extrusion has been successfully applied to produce a batch of about 10 kg of ODS steel. Full size ASTM E21 and E8 specimens have been tested from room temperature up to 800 °C. The microstructure characterization of the manufactured materials has been carried out by transmission electron microscopy. Ultimate tensile stress higher than 1350 MPa have been obtained in the as-extruded material and higher than 1100 MPa in samples annealed for 4 hours at 800 °C.

Fine Microstructure of a Mechanically Alloyed Oxide Dispersion Strengthened Nickel-Base Superalloy

1977 ◽  
Vol 35 ◽  
pp. 298-299
Author(s):  
Jordi Marti ◽  
Timothy E. Howson ◽  
David Kratz ◽  
John K. Tien
Keyword(s):  
Solid Solution ◽  
Volume Fraction ◽  
Stress Rupture ◽  
Oxide Dispersion Strengthened ◽  
Solid Solution Alloy ◽  
Oxide Dispersion ◽  
Creep And Stress Rupture ◽  
Mechanically Alloyed ◽  
Fine Microstructure ◽  
Nickel Base

The previous paper briefly described the fine microstructure of a mechanically alloyed oxide dispersion strengthened nickel-base solid solution. This note examines the fine microstructure of another mechanically alloyed system. This alloy differs from the one described previously in that it is more generously endowed with coherent precipitate γ forming elements A1 and Ti and it contains a higher volume fraction of the finely dispersed Y2O3 oxide. An interesting question to answer in the comparative study of the creep and stress rupture of these two ODS systems is the role of the precipitate γ' in the mechanisms of creep and stress rupture in alloys already containing oxide dispersoids.The nominal chemical composition of this alloy is Ni - 20%Cr - 2.5%Ti - 1.5% A1 - 1.3%Y203 by weight. The system receives a three stage heat treatment-- the first designed to produce a coarse grain structure similar to the solid solution alloy but with a smaller grain aspect ratio of about ten.

scholarly journals Microstructure, Grain Growth and Hardness of Nanostructured Ferritic ODS Steel Powder during Annealing

2021 ◽  
Author(s):  
Krzysztof Nowik ◽  
Zbigniew Oksiuta
Keyword(s):  
Dislocation Density ◽  
Size Distribution ◽  
Hot Isostatic Pressing ◽  
Domain Size ◽  
Oxide Dispersion Strengthened ◽  
Alloy Formation ◽  
Nanocrystalline State ◽  
Ferritic Alloy ◽  
Ods Steel ◽  
Double Phase

AbstractNanocrystalline oxide-dispersion strengthened ferritic alloy formation and its annealing behavior were examined through modern X-ray diffraction pattern analysis and supplemented by microhardness and microscopic measurements. The basic microstructure features, with particular emphasis on evolution of domain size distribution and defect content during mechanical and thermal treatment, were quantified via the whole powder pattern modeling approach. The microstructure of the powdered alloy, formed during mechanical alloying, evolved toward nanocrystalline state consisting of narrow dispersion of very fine crystallites with substantial dislocation density, which exhibited relatively high stability against elevated temperature. It was shown that crystallite size is seriously sustained by the grain-boundary strain, therefore coarsening of grains begins only after the density of dislocations drops below certain level. Obtaining correct results for the annealing-related data at specific temperature range required the incorporation of the “double-phase” model, indicating possible bimodal domain size distribution. The dislocation density and grain size were found not to be remarkably affected after consolidation by hot isostatic pressing.

Characterization of oxide particles in ODS austenitic stainless steel after heavy ion irradiation up to high doses

2011 ◽  
Vol 1298 ◽  
Author(s):  
Hiroshi Oka ◽  
Yosuke Yamazaki ◽  
Hiroshi Kinoshita ◽  
Naoyuki Hashimoto ◽  
Somei Ohnuki ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Ion Irradiation ◽  
Hot Extrusion ◽  
Oxide Dispersion Strengthened ◽  
Complex Oxide ◽  
Heavy Ion ◽  
Oxide Particles ◽  
The Difference ◽  
High Doses

ABSTRACTOxide dispersion strengthened austenitic stainless steel (ODS316), which is based on advanced SUS316 steel, has been developed by mechanically alloying and hot extrusion. Hafnium and titanium were added to make a fine distribution of oxide particles. The stability of oxide particles dispersed in ODS316 under irradiation was evaluated after 250 keV Fe+ irradiation up to high doses at 500 °C. TEM observation and EDS analysis indicated that fine complex oxide particles with Y, Hf and Ti were mainly dispersed in the matrix. There are no significant changes in the distribution and the size of oxide particles after irradiation. It was also revealed that the constitution ratio of Ti in complex oxide appeared to be decreased after irradiation. This diffuse-out of Ti during irradiation could be explained by the difference in oxide formation energy among alloying elements.

Effect of Temperature on the Structure and Mechanical Properties of Mechanically Alloyed Al-Nio Composite

2014 ◽  
Vol 59 (1) ◽  
pp. 121-126
Author(s):  
M. Zygmunt-Kiper ◽  
L. Blaz ◽  
M. Sugamata
Keyword(s):  
Mechanical Properties ◽  
Aluminum Oxide ◽  
Aluminum Matrix ◽  
Hot Extrusion ◽  
Effect Of Temperature ◽  
Compression Tests ◽  
Mechanically Alloyed ◽  
Structure Morphology ◽  
High Purity Aluminum ◽  
Extrusion Method

Abstract Mechanical alloying of high-purity aluminum and 10 wt.% NiO powders combined with powder vacuum compression and following hot extrusion method was used to produce an Al-NiO composite. Mechanical properties of as-extruded materials as well as the samples annealed at 823 K /6 h, were tested by compression at 293 K - 770 K. High mechanical properties of the material were attributed to the highly refined structure of the samples. It was found that the structure morphology was practically not changed during hot-compression tests. Therefore, the effect of deformation temperature on the hardness of as-deformed samples was very limited. The annealing of samples at 823 K/6 h induced a chemical reaction between NiO-particles and surrounding aluminum matrix. As a result, the development of very fine aluminum oxide and Al3Ni grains was observed.

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