Analytical characterization of secondary phases and void distributions in an ultrafine-grained ODS Fe─14Cr model alloy

Proceedings of the: The 14th International Conference on Fusion Reactor Materials (ICFRM-14) was held at the Sapporo Convention Center in Sapporo, Japan from 7 to 12 September 2009.Two model Fe─14Cr alloys, one containing 0.3 wt.% of Y₂O₃ particles, were fabricated by mechanical alloying of Fe and Cr elemental powders under a He atmosphere. They were subsequently consolidated and thermomechanically treated to produce ultra-fine grained materials. Cr-carbides and oxides were found in both alloys. The oxide dispersion-strengthened (ODS) alloy also contained a fine dispersion of nanoparticles, some of them having a Y─O rich core and a Cr-rich shell. Nanometric sized voids were found in both materials, often attached to secondary phases, dislocations and grain boundaries. Their sizes were significantly smaller in the ODS alloy.This research has been supported by the Fusion Energy Materials Science (FEMaS) FP7 coordination action and the IP3 FP6 ESTEEM project under Contract No. 026019. The financial support from European Fusion Development Agreement (Contract No. 09-240), the Ministerio de Innovacion y Ciencia (Project No. ENE 2008-06403-C06-04 and Juan de la Cierva programme) and the Comunidad de Madrid, through the program ESTRUMAT-CM, Grant S-0505/MAT/0077Publicad

Microstructure and mechanical behavior of ODS and non-ODS Fe-14Cr model alloys produced by spark plasma sintering

In this work the spark plasma sintering (SPS) technique has been explored as an alternative consolidation route for producing ultra-fine grained Fe–14Cr model alloys containing a dispersion of oxide nanoparti-cles. Elemental powders of Fe and Cr, and nanosized Y₂O₃ powder have been mechanically alloyed in a planetary ball mill and rapidly sintered in a spark plasma furnace. Two alloys, with nominal compositions Fe–14%Cr and Fe–14% Cr–0.3%Y₂O₃ (wt.%), have been fabricated and their microstructure and mechanical properties investigated. The results have been compared with those obtained for other powder metal-lurgy processed alloys of the same composition but consolidated by hot isostatic pressing. The SPS tech-nique under the present conditions has produced Fe–14Cr materials that apparently exhibit different microstructures yielding inferior mechanical properties than the counterpart material consolidated by hot isostatic pressing. Although the presence of a dispersion of Y-rich particles is evident, the oxide dis-persion strengthened (ODS) Fe–14Cr alloy consolidated by SPS exhibits poor tensile properties. The extensive decoration of the powder particle surfaces with Cr-rich precipitates and the residual porosity appear to be responsible for the impaired properties of this ODS alloy consolidated by SPS.This investigation was supported by the Ministry of Science and Innovation of Spain (Project No. ENE 2008-06403-C06-04), the Comunidad de Madrid through the program ESTRUMAT-CM(Grant No. S0505/MAT/0077), and the European Commission through the European Fusion Development Agreement (Contract No. 09-240), the IP3 FP6 ESTEEM project (Contract No. 026019) and the Fusion Energy Materials Science (FEMaS) FP7 coordination action.Publicad

Characterization of novel W alloys produced by HIP

Proceedings of: The Thirteenth International Conference on Fusion Reactor, Nice (France), 10–14 December 2007.W and W alloys containing 0.5 wt% Y₂O₃, x wt% Ti and (x wt% Ti + 0.5 wt% Y₂O₃) have been prepared, x 2 or 4. Elemental powders were blended or ball milled, canned, degassed and finally consolidated by a two stage HIP process under a pressure of 195 MPa. It is found that Ti addition favours the densification attaining a fully dense material. XRD, SEM and EDX analyses of the material with Ti addition reveal the formation of a microstructure consisting of tungsten particles embedded in a W Ti matrix. The microhardness of these materials increased noticeably with the titanium content.Dirección General de Investigación (Ministry of Education of Spain, Contract MAT2004 1819), the Dirección General de Universidades (Comunidad de Madrid) through the program of ESTRUMAT CM (Grant S 0505/MAT/0077) and EURATOM/CIEMAT Association through Contract 07/006.Publicad

Microstructural and mechanical characteristics of EUROFER'97 processed by equal channel angular pressing

Proceedings of : 14th International Conference on Fusion Reactor Materials (ICFRM-14), 6-11 september, 2009. Sapporo Convention Center Sapporo, Japan.EUROFER'97 was processed by equal channel angular pressing (ECAP) at 823 K for a total of 4 or 8 passes, using a die angle of 105°, and its microstructure and tensile behavior in temperature range 568 873 K investigated. A single ECAP pass developed a deformation texture {1 1 0} 〈0 1 1〉 that was practically stable during subsequent ECAP passes. The materials processed by 1 or 2 passes exhibited a fine microstructure of recovered subgrains and tensile behavior very similar to that for the tempered material in the as-received condition. The materials processed using 4 or 8 passes exhibited nearly equiaxial submicron grained structures with a high density of high-angle grain boundaries. These materials became softer than the as-received material at a testing temperature of ~8764;823 K. EUROFER ECAP processed under the present conditions exhibited hardening ratio somewhat higher than that of the as-received material.This investigation was supported by the EURATOM/CIEMAT association through Contract 09 240, by the Comunidad de Madrid (program ESTRUMAT CM S0505/MAT/0077) and by Spanish Ministry of Science and Innovation Contract ENE 2008 06403 C06 04.Publicad

Analytical characterisation of oxide dispersion strengthened steels for fusion reactors

Special issue articleReduced activation ferritic/martensitic and ferritic steels strengthened by a dispersion of oxide nanoparticles have been considered viable structural materials for fusion applications above 550°C. However, the microstructural stability and mechanical behaviour of these steels subjected to the aggressive operating conditions of these reactors are not well known. An accelerated development of these materials is crucial if they are going to be used in future power reactors. Then, it is indispensable to understand their atomic scale evolution under high temperature and irradiation conditions. The present paper reviews how the combination of transmission electron microscopy and atom probe tomography has been successfully applied for the characterisation of these steels at the near atomic scale, to reveal the nanoparticle structure, grain boundary chemistry and void distribution.The present research has been supported by the FP6 Euratom Research and Training Programme on Nuclear Energy, the Fusion Energy Materials Science (FEMaS) FP7 coordination action, the IP3 FP6 ESTEEM project under contract no. 026019 and the Consejería de Educación de la Comunidad de Madrid, through the program ESTRUMAT-CM S2009MAT-1585. EAM thanks the Royal Society for the financial support (RS Dorothy Hodgkin fellowship)

Microstructure and tensile properties of oxide dispersion strengthened Fe–14Cr– 0.3Y₂O₃ and Fe–14Cr–2W–0.3Ti–0.3Y₂O₃

Proocedings of: 15th International Conference on Fusion Reactor Materials (ICFRM15). Charleston, South Carolina (United States of America), 16-22 october, 2011Two ODS ferritic steels with nominal compositions (wt.%): Fe–14Cr–0.3Y2O3 and Fe–14Cr–2W–0.3Ti–0.3Y2O3 have been produced by mechanical alloying and consolidation by hot isostatic pressing. The microstructure and tensile properties of these materials after being forged and heat treated at 1123 K have been investigated to clarify the interrelation between composition, microstructure and mechanical properties. The second phase precipitates in these alloys have been analyzed by high angle annular dark field imaging in scanning TEM mode and electron diffraction. Fe–14Cr–2W–0.3Ti–0.3Y2O3 exhibits a duplex microstructure consisting of large recrystallized grains, as large as 1.5 μm, and unrecovered regions containing submicron equiaxed grains. In addition, three types of secondary phase particles have been found: large M₂₃C₆ particles containing W and Cr, (Cr + Ti) rich spherical particles with diameters between 50 and 500 nm, and fine (Y + Ti) oxide particles with sizes below 30 nm. In contrast, Fe14CrY shows a uniform structure of equiaxed grains, with sizes in the range 0.5 3 μm, containing a fine disper sion of Y oxide particles (<30 nm) homogeneously distributed inside the grains, as well as large carbide and oxide particles. Tensile tests performed over the temperature range 273 973 K have revealed that the alloy containing W and Ti has lower yield and tensile strengths than Fe–14Cr–0.3Y2O3 at tempera tures up to 773 K, but the opposite appears to occur beyond this temperature.This investigation was supported by the Spanish Ministry of Science and Innovation (Project No. ENE 2008 06403 C06 04 and Juan de la Cierva program), the Comunidad de Madrid through the program ESTRUMAT CM (Grant S0505/MAT/0077), and the European Commission through the European Fusion Development Agreement (Contract No. 09 240), the IP3 FP6 ESTEEM project (Contract No. 026019) and the Fusion Energy Materials Science (FEMaS) FP7 coordination action.Publicad

Microstructure and mechanical properties of ultrafine-grained Fe─14Cr and ODS Fe─14Cr model alloys

This study is to: The 14th International Conference on Fusion Reactor Materials (ICFRM-14) was held at the Sapporo Convention Center in Sapporo, Japan from 7 to 12 September 2009Reduced activation ferritic Fe─14 wt%Cr and Fe─14 wt%Cr─0.3 wt%Y₂O₃ alloys were produced by mechanical alloying and hot isostatic pressing followed by forging and heat treating. The alloy containing Y₂O₃ developed a submicron-grained structure with homogeneous dispersion of oxide nanoparticles that enhanced the tensile properties in comparison to the Y₂O₃ free alloy. Strengthening induced by the Y₂O₃ dispersion appears to be effective up to 873 K, at least. A uniform distribution of Cr-rich precipitates, stable upon a heat treatment at 1123 K for 2 h, was also found in both alloys.This investigation was supported by the Spanish Ministry of Science and Innovation (project No ENE 2008-06403-C06-04 and Juan de la Cierva program), the Comunidad de Madrid through the program ESTRUMAT-CM (grant S0505/MAT/0077), and the European Commission through the European Fusion Development Agreement (contract No. 09-240), the IP3 FP6 ESTEEM project (contract No. 026019) and the Fusion Energy Materials Science (FEMaS) FP7 coordination action.Publicad

Microstructural characterization of Y₂O₃ ODS-Fe-Cr model alloys

Proceedings of the: Thirteenth International Conference on Fusion Reactor Materials. Nice (France), 10-14/12/2007.Two Fe-12 wt% Cr alloys, one containing 0.4 wt% Y₂O₃ and the other Y₂O₃ free, have been produced by mechanical alloying followed by hot isostatic pressing. These oxide dispersion strengthened and reference alloys were characterized both in the as-HIPed state and after tempering by transmission electron microscopy and atom-probe tomography. The as-HIPed alloys exhibited the characteristic microstructure of lath martensite and contained a high density of dislocations. Small voids with sizes <10 nm were also observed. Both alloys also contained M₃C and M₂₃C₆ carbides (M = Cr, Fe) probably as a result of C ingress during milling. After tempering at 1023 K for 4 h the microstructures had partially recovered. In the recovered regions, martensite laths were replaced by equiaxed grains in which M₂₃C₆ carbides decorated the grain boundaries. In the ODS alloy nanoparticles containing Y were commonly observed within grains, although they were also present at grain boundaries and adjacent to large carbides.This research has been supported by FP6 Euratom Research and Training Programme on Nuclear Energy. The financial support from the Comunidad de Madrid, through the program ESTRUMAT CM,Grant S 0505/MAT/0077.Publicad

Review on the EFDA work programme on nano-structured ODS RAF steels

This proceeding is: The 14th International Conference on Fusion Reactor Materials (ICFRM-14) was held at the Sapporo Convention Center in Sapporo, Japan from 7 to 12 September 2009.The 2008─2009 work programme of the European research project on nano-structured oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steels is being organized along the four following programmatic lines: (1) improve the present generation of nano-structured ODS RAF steels; (2) start the industrial fabrication of the present generation of nano-structured ODS RAF steels; (3) develop an optimised generation of nano-structured and nano-grained ODS RAF steels; (4) investigate the stability of present and optimised generation of nano-structured ODS RAF steels under creep and irradiation. This paper presents the main objectives of current R&D activities being performed within the European research project on nano-structured ODS RAF steels, the main obtained results and the main future activities in the case of the four programmatic lines mentioned just above.This work, supported by the European Communities, was carried out within the framework of the European Fusion Development Agreement.Publicad

Caracterización mineralógica y química de los ladrillos de la Torre del Oro de Sevilla: una aproximación a la temperatura de cocción y origen de las materias primas

The Torre del Oro is a Moslem building of three bodies dating from the 13th Century. The second and third bodies are built with bricks. According to mineralogical analysis two main groups of bricks can be established. A first group of bricks contents illite and low amounts of gehlenite and wollastonite. They are reddish and present a mycrocristalline matrix. The firing temperature ranges between 800-850ºC for this group. Firing temperatures for the second group ranged between 850-900ºC, because of the absence of illite, and the presence of important amounts of gehlenite and wollastonite-diopside. They are yellowish and present a green coloured isotropic matrix. Mineralogical compositions of laboratory firing samples at 800ºC and 900ºC agree reasonably with the estimated firing temperature. Chemical composition presents no differences among the samples, being quite similar to Tertiary sediments from the Ecija Formation (blue marls) and the Transition Series (silts). These materials crop out quite near Seville, and have been traditionally used in the local tile industry.&lt;br&gt;&lt;br&gt;La Torre del Oro es un edificio almohade del siglo XIII de tres cuerpos, con fábrica de ladrillo en el segundo y tercer cuerpo. De acuerdo con el análisis mineralógico se han diferenciado dos grupos de ladrillos. El primero se caracteriza por la presencia de illita y el desarrollo incipiente o nulo de fases de alta temperatura (gehlenita, wollastonita). Presentan coloraciones rojizas y pasta con textura microcristalina. Estos ladrillos se cocieron entre 800-850ºC. Para el segundo grupo la temperatura de cocción se encuentra entre 850-900ºC, según se deduce de la ausencia de illita y de la presencia en cantidades importantes de gehlenita y wollastonita-diopsido. La pasta es verde oscura e isótropa, presentando los ladrillos colores claros. El estudio de la evolución de las fases en los ladrillos calentados en el laboratorio a 800 y 900ºC concuerda razonablemente con los márgenes de cocción deducidos del estudio mineralógico. La composición química de los ladrillos es muy homogénea y similar a la de los materiales terciarios de la Formacion Écija (margas azules) y de ciertos niveles de la Serie de Transición, ambos con afloramientos muy próximos a Sevilla, que pudieron ser empleados para la fabricación de estos ladrillos