ODS-materials for high temperature applications in advanced nuclear systems

AbstractA ferritic ODS-alloy (Fe-14Cr-1W-0.25Ti) has been manufactured by application of the powder metallurgical production route involving at first mechanical alloying of ∼10kg pre-alloyed steel powder together with an Y2O3 addition for 12h in a high energy industrial ball mill under hydrogen atmosphere at the company ZOZ GmbH. As a next step, one part of the alloyed powder was hot extruded into rods while another portion was hot isostatically pressed into plates. Both materials were then heat treated. A characterization program on these ODS-alloy production forms included microstructural and mechanical investigations: SANS and TEM assume the existence of Y2Ti2O7 nano clusters and show a bimodal distribution of ODS-particle sizes in both ODS variants. EBSD maps showed a strong 〈110〉 texture corresponding to the α fiber for the hot extruded ODS and a slight 〈001〉 texture for the hipped ODS material. Fracture toughness tests in different specimen orientations (extruded ODS) with mini 0.2T C(T) specimens together with Charpy impact tests revealed anisotropic mechanical properties: Promising (fracture) toughness levels were obtained in the specimen orientation perpendicular to the extrusion direction, while the toughness levels remained low in extrusion direction and generally for the hipped ODS material at all test temperatures. The fracture toughness tests were performed according to ASTM E 1921 and 1820 standards

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

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

Nano-scale chemical evolution in a proton-and neutron-irradiated Zr alloy

Proton-and neutron-irradiated Zircaloy-2 are compared in terms of the nano-scale chemical evolution within second phase particles (SPPs) Zr(Fe,Cr)2 and Zr2(Fe,Ni). This is accomplished through ultra-high spatial resolution scanning transmission electron microscopy and the use of energy-dispersive X-ray spectroscopic methods. Fe-depletion is observed from both SPP types after irradiation with both irradiative species, but is heterogeneous in the case of Zr(Fe,Cr)2, predominantly from the edge region, and homogeneously in the case of Zr2(Fe,Ni). Further, there is evidence of a delay in the dissolution of the Zr2(Fe,Ni) SPP with respect to the Zr(Fe,Cr)2. As such, SPP dissolution results in matrix supersaturation with solute under both irradiative species and proton irradiation is considered well suited to emulate the effects of neutron irradiation in this context. The mechanisms of solute redistribution processes from SPPs and the consequences for irradiation-induced growth phenomena are discussed.<br/

Design, Biomimética e Transdisciplinariedade: Estratégias Sustentáveis com foco na Inovação

Nos últimos anos, a exploração da ciência Biomimética como potencial fonte de inovação tem sido alvo de um investimento crescente por parte de investigadores e profissionais de diversas áreas. O presente artigo aborda o tema da aplicação de processos Biomiméticos ao Design, tendo como base matricial o alcance de resultados BioEco-Inovadores. Por outro lado, não obstante a sua emergência - particularmente no contexto da oferta formativa superior em Design -, o processo de trabalho efetivamente transdisciplinar é atualmente assumido como motor fomentador de maior criatividade e de mais oportunidades de inovação. É assim propósito deste artigo, contribuir para a reflexão crítica sobre a delimitação e aplicação de métodos transdisciplinares de inovação, explorados em processo de Design, que se afirmem como promotores de BioEco-Inovação, segundo modelos passíveis de serem integrados académica e profissionalmente. Com vista à construção de soluções artificiais sustentáveis, mais próximas das estratégias de eficácia e de eficiência da própria natureza, pretende-se com esta proposta colaborar para a gradual integração de práticas biomiméticas transdisciplinares, na formação de futuros e de atuais designers