Effect of mechanical alloying atmosphere on the microstructure and Charpy impact properties of an ODS ferritic steel

Nadine Baluc, Zbigniew Oksiuta
Elsevier, 2009
Conference paper

Two types of oxide dispersion strengthened (ODS) ferritic steels, with the composition of Fe-14Cr-2W-0.3Ti-0.3Y(2)O(3) (in weight percent), have been produced by mechanically alloying elemental powders of Fe, Cr, W, and Ti with Y2O3 particles either in argon atmosphere or in hydrogen atmosphere, degassing at various temperatures, and compacting the mechanically alloyed powders by hot isostatic pressing. It was found in particular that mechanical alloying in hydrogen yields a significant reduction in oxygen content in the materials, a lower dislocation density, and a strong improvement in the fast fracture properties of the ODS ferritic steels, as measured by Charpy impact tests. (C) 2009 Elsevier B.V. All rights reserved.

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Nadine Baluc, Zbigniew Oksiuta
Elsevier, 2009
Conference paper

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https://infoscience.epfl.ch/record/148900?ln=en

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Microstructure and mechanical properties of an ODS RAF steel fabricated by hot extrusion or hot isostatic pressing

Nadine Baluc, Zbigniew Oksiuta

Ingots of an oxide dispersion strengthened reduced activation ferritic steel with the Fe-14Cr-2W-0.3Ti-0.3Y(2)O(3) chemical composition (in wt.%) were synthesized by mechanical alloying of elemental powders with 0.3 wt.% Y2O3 particles in a planetary ball mill, in a hydrogen atmosphere. and compacted by either hot extrusion or hot isostatic pressing. The microstructures of the obtained materials were characterized by means of light microscopy, transmission electron microscopy and chemical analyses. The mechanical properties were evaluated by means of Vickers microhardness measurements and tensile tests. It was found that the microstructure of both materials is composed of ferritic grains having a submicron size and containing nanometric Y-Ti-O oxide particles with a mean size of about 10 nm, uniformly distributed in the matrix. The oxide particles in the hot extruded steel were identified as YTiO3 phase. In larger (>10 nm) oxide particles Cr was found next to Ti, Y and O. The steel produced by hot extrusion exhibits much higher tensile strength and hardness at low to moderate temperatures, as compared to the steel fabricated by hot isostatic pressing, which was mainly attributed to smaller pores but also to more severe work hardening in the case of the hot extruded steel. (C) 2011 Elsevier B.V. All rights reserved.

2011

Processing and characterization of a W–2Y material for fusion power reactors

Nadine Baluc, Robin Schäublin, Lyubomira Veleva

A W-2Y material has been produced by powder metallurgy techniques including mechanical alloying of W and Y elemental powders in an argon atmosphere, followed by hot isostatic pressing of the milled powder at 1320 degrees C under a pressure of 200 MPa for 2 h. It was found that the mechanical alloying time should not exceed 40 h in order to achieve a homogeneous distribution of small powder particles and to limit air contamination and carbon/WC contamination by the jar and ball materials. The density of the ingots was found to be about 97% the theoretical one. It was observed that the microstructure of the compacted material is composed of grains having a bimodal size distribution, with mean sizes around 50 and 150 nm. In addition, the material contains an inhomogeneous distribution of oxide particles with a mean size ranging from 2 to 20 nm. In situ TEM chemical analyses revealed that the entire content of yttrium reacted with oxygen to form nanometric oxides whose composition corresponds to Y2O3. Charpy impact tests revealed that the material is brittle at the high temperature of about 1000 degrees C. Tensile tests confirmed that the material is brittle at 1000 degrees C but ductile at 1300 degrees C, indicating that the ductile-to-brittle transition temperature should lie between 1100 and 1200 degrees C. (C) 2011 EURATOM associated institution EPFL CRPP. Published by Elsevier B.V. All rights reserved.

Elsevier2011

Development and characterisation of a new ODS ferritic steel for fusion reactor application

Nadine Baluc, Zbigniew Oksiuta

This paper describes the microstructure, tensile properties and Charpy impact resistance of a reduced activation oxide dispersion strengthened ferritic steel Fe-14Cr-2W-0.3Ti-0.3Y(2)O(3) produced by mechanical alloying of a pre-alloyed, gas atomised steel powder with Y2O3 particles, compaction by hot extrusion at 1100 degrees C, hot rolling at 700 degrees C and heat treatment at 1050 degrees C for 1 h. At room temperature the material exhibits a high ultimate tensile strength of about 1420 MPa and high yield strength of about 1340 MPa in the transverse direction. In the longitudinal direction the values are about 10% lower, due to the anisotropy of the microstructure (elongated grains in the rolling direction). At 750 degrees C the material still exhibits relatively high yield strengths of about 325 MPa and 305 MPa in the longitudinal and transverse directions, respectively. The material exhibits reasonable uniform and total elongation values over the temperature range 23-750 degrees C, in both transverse and longitudinal directions. The material exhibits weak Charpy impact properties in the transverse direction. Charpy impact properties are slightly better in the longitudinal direction, with upper shelf energy of about 4.2 J and a ductile-to-brittle transition temperature of about 8.8 degrees C. (C) 2009 Elsevier B.V. All rights reserved.

Elsevier2009

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Rights are legal, social, or ethical principles of freedom or entitlement; that is, rights are the fundamental normative rules about what is allowed of people or owed to people according to some legal

Charpy impact test

In materials science, the Charpy impact test, also known as the Charpy V-notch test, is a standardized high strain rate test which determines the amount of energy absorbed by a material during fract

Human rights

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