Este trabalho consiste em uma pesquisa sobre aços inoxidáveis ferríticomartensíticos de ativação ... more Este trabalho consiste em uma pesquisa sobre aços inoxidáveis ferríticomartensíticos de ativação reduzida (RAFM): EUROFER (9Cr-1W) e ODS-EUROFER (9Cr-1W-0,3Y2O3), envolvendo o encruamento e a recristalização destas duas ligas com o objetivo de estudar a influência de uma dispersão de partículas nanométricas na recristalização de aços inoxidáveis. O conceito de materiais de ativação reduzida é discutido e é apresentada a aplicação destes aços tanto na estrutura de diversor do ITER quanto na primeira parede no módulo de câmara fértil do reator DEMO. As placas, no estado revenido, foram laminadas a frio em um laminador de pequeno porte. As curvas de encruamento de ambos os materiais mostram um comportamento quase linear. Os tratamentos isócronos de uma hora, entre 300 e 750 °C, resultaram curvas de amolecimento que indicam uma forte resistência à recristalização da liga ODS-EUROFER, em concordância com os modelos teóricos. A liga EUROFER-97 apresentou recristalização muito similar a li...
Reduced activation ferritic-martensitic steels are considered for future applications in fusion p... more Reduced activation ferritic-martensitic steels are considered for future applications in fusion power plants. The thermal stability of two steels (ODS-Eurofer and Eurofer-97) was evaluated in cold-rolled samples annealed below 800°C. These grades have similar chemical compositions except for the presence of nanosized Y2O3 particles in ODS-Eurofer steel. This nanosized dispersion is very effective to prevent recrystallization. On the other hand, full recrystallization occurs in Eurofer-97 steel when annealed above 700°C. The low volume fraction of recrystallized grains (< 0.1) in ODS-Eurofer steel annealed at 800°C can be explained by nucleation at prior grain boundaries and around large M23C6 particles. Further growth of these nuclei is impeded by Zener drag and concurrent recovery. Static recovery is the main softening mechanism in the ODS-steel below 800°C.
In the present work, the corrosion resistance of ferritic-martensitic EUROFER 97 and ODS-EUROFER ... more In the present work, the corrosion resistance of ferritic-martensitic EUROFER 97 and ODS-EUROFER steels was tested in solutions containing NaCl or H2SO4 and KSCN, both at 25 °C. The results were compared to those of AISI 430 ferritic and AISI 410 martensitic conventional stainless steels. The as-received samples were tested by electrochemical techniques, specifically, electrochemical impedance spectroscopy, potentiodynamic polarization curves, and double-loop electrochemical potentiokinetic reactivation tests. The surfaces were observed by scanning electron microscopy after exposure to corrosive media. The results showed that EUROFER 97 and ODS-EUROFER alloys present similar corrosion resistance but lower than ferritic AISI 430 and martensitic 410 stainless steels.
Este trabalho consiste em uma pesquisa sobre aços inoxidáveis ferríticomartensíticos de ativação ... more Este trabalho consiste em uma pesquisa sobre aços inoxidáveis ferríticomartensíticos de ativação reduzida (RAFM): EUROFER (9Cr-1W) e ODS-EUROFER (9Cr-1W-0,3Y2O3), envolvendo o encruamento e a recristalização destas duas ligas com o objetivo de estudar a influência de uma dispersão de partículas nanométricas na recristalização de aços inoxidáveis. O conceito de materiais de ativação reduzida é discutido e é apresentada a aplicação destes aços tanto na estrutura de diversor do ITER quanto na primeira parede no módulo de câmara fértil do reator DEMO. As placas, no estado revenido, foram laminadas a frio em um laminador de pequeno porte. As curvas de encruamento de ambos os materiais mostram um comportamento quase linear. Os tratamentos isócronos de uma hora, entre 300 e 750 °C, resultaram curvas de amolecimento que indicam uma forte resistência à recristalização da liga ODS-EUROFER, em concordância com os modelos teóricos. A liga EUROFER-97 apresentou recristalização muito similar a li...
Reduced activation ferritic-martensitic steels are considered for future applications in fusion p... more Reduced activation ferritic-martensitic steels are considered for future applications in fusion power plants. The thermal stability of two steels (ODS-Eurofer and Eurofer-97) was evaluated in cold-rolled samples annealed below 800°C. These grades have similar chemical compositions except for the presence of nanosized Y2O3 particles in ODS-Eurofer steel. This nanosized dispersion is very effective to prevent recrystallization. On the other hand, full recrystallization occurs in Eurofer-97 steel when annealed above 700°C. The low volume fraction of recrystallized grains (< 0.1) in ODS-Eurofer steel annealed at 800°C can be explained by nucleation at prior grain boundaries and around large M23C6 particles. Further growth of these nuclei is impeded by Zener drag and concurrent recovery. Static recovery is the main softening mechanism in the ODS-steel below 800°C.
In the present work, the corrosion resistance of ferritic-martensitic EUROFER 97 and ODS-EUROFER ... more In the present work, the corrosion resistance of ferritic-martensitic EUROFER 97 and ODS-EUROFER steels was tested in solutions containing NaCl or H2SO4 and KSCN, both at 25 °C. The results were compared to those of AISI 430 ferritic and AISI 410 martensitic conventional stainless steels. The as-received samples were tested by electrochemical techniques, specifically, electrochemical impedance spectroscopy, potentiodynamic polarization curves, and double-loop electrochemical potentiokinetic reactivation tests. The surfaces were observed by scanning electron microscopy after exposure to corrosive media. The results showed that EUROFER 97 and ODS-EUROFER alloys present similar corrosion resistance but lower than ferritic AISI 430 and martensitic 410 stainless steels.
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Papers by Angelo Zimmermann