Fernando Rizzo - Academia.edu (original) (raw)
Papers by Fernando Rizzo
Materials Science and Engineering: A, 2015
The purpose of this paper is to reveal the dominant factors affecting tensile fracture under a hy... more The purpose of this paper is to reveal the dominant factors affecting tensile fracture under a hydrogen gas atmosphere. Tensile tests were conducted in hydrogen gas with circumferentially-notched specimens of a commercial tempered martensitic steel. Two specimens were exposed to hydrogen gas for 48 h before tensile testing; the other two specimens were not pre-charged. Longitudinal cracks along the loading direction and a transverse crack perpendicular to the loading direction were observed on a cross section of the non-charged specimen, but there was only one small crack on a cross section of the precharged specimen. Electron back scatter diffraction, energy dispersive X-ray spectrometry and finite element method analyses were applied to clarify the relationships among the longitudinal crack, Mn segregation, microstructures of martensitic steel and hydrogen. As a result, it has been demonstrated that Mn segregation and MnS promote hydrogen-assisted cracking in the tempered martensitic steel, causing the longitudinal cracking which is a mechanically non-preferential direction in homogeneous situations. More specifically, we have shown that the role of the Mn segregation is to promote the hydrogen-enhanced decohesion effect (HEDE), which is particularly important for crack propagation in the present case. These considerations indicate that the presence of Mn is crucially important for hydrogen-assisted cracking associated with hydrogen-enhanced localized plasticity (HELP) as well as HEDE.
Journal of Materials Research and Technology, 2021
Soldagem & Inspeção (Impresso), 2010
Com o objetivo de fornecer subsídios para a seleção de consumíveis para a soldagem molhada foram ... more Com o objetivo de fornecer subsídios para a seleção de consumíveis para a soldagem molhada foram determinadas algumas propriedades do metal de solda a partir de juntas soldadas em água doce com eletrodos revestidos comerciais específicos para este fim. As soldas foram realizadas em tanque a 0,5m de profundidade por dispositivo de soldagem por gravidade. Foram levantados dados que auxiliem a eleger os consumíveis de melhor desempenho para serem testados em maiores profundidades. Foram realizados os seguintes testes e avaliações: caracterização microestrutural, análise e quantificação das inclusões, composição química do metal de solda, dureza Vickers, hidrogênio difusível e avaliação da soldabilidade. Os resultados obtidos permitem classificar os consumíveis testados em dois grupos com características bem distintas. No primeiro grupo está o único eletrodo do tipo oxidante e no segundo grupo estão os quatro eletrodos do tipo rutílico testados. Quanto às propriedades mecânicas e às car...
JOM, 2017
The path of society evolution has long been associated with a growing demand for natural resource... more The path of society evolution has long been associated with a growing demand for natural resources and continuous environmental degradation. During the last decades, this pace has accelerated considerably, despite the general concern with the legacy being left for the next generations. Looking ahead, the predicted growth of the world population, and the improvement of life conditions in most regions, point to an increasing demand for energy generation, resulting in additional pressure on the Earth’s sustainability. Materials have had a key role in decreasing the use of natural resources, by either improving efficiency of existing technologies or enabling the development of radical new ones. The greenhouse effect (CO2 emissions) and the energy crisis are global challenges that can benefit from the development of new materials for the successful implementation of promising technologies and for the imperative replacement of fossil fuels by renewable sources.
Soldagem & Inspeção, 2013
A técnica de soldagem subaquática molhada com eletrodos revestidos apresenta um crescente potenci... more A técnica de soldagem subaquática molhada com eletrodos revestidos apresenta um crescente potencial de aplicação para reparos submarinos em elementos estruturais de unidades flutuantes de produção de petróleo (profundidade até 20 m). Porém, ela apresenta problemas tais como o maior risco de fissuração a frio e de formação acentuada de porosidade. O presente trabalho tem como objetivo melhorar a resistência mecânica do metal de solda de um eletrodo experimental do tipo oxi-rutílico. Foram estudadas as influências de adições de Mo (até 0,4% no metal de solda) na microestrutura e em propriedades mecânicas. As soldas foram realizadas em simulador de soldagem subaquática em profundidade equivalente de 10m utilizando um sistema de soldagem por gravidade. As análises das micrografias mostrou que o aumento do teor de Mo no metal de solda diminui significantemente o tamanho médio de grão da região reaquecida de grãos finos. O aumento do teor de Mo no metal de solda resultou, ainda, em aument...
Tecnologia em Metalurgia e Materiais, 2006
Tecnologia em Metalurgia e Materiais, 2005
Tecnologia em Metalurgia e Materiais, 2004
Tecnologia em Metalurgia e Materiais, 2007
Tecnologia em Metalurgia e Materiais, 2004
The development of cooperative research networks requires the collaboration among partners with d... more The development of cooperative research networks requires the collaboration among partners with different visions about the timing and goals of a research project. In some cases, even competitors are invited to take part in the same initiative, making ground to lack of communication and/or loss of interest in the outcome of the research. During the establishment of the Metal/Mechanics network of the RECOPE program, one large step toward the increase of interaction and collaboration was achieved through one sequence of meetings and short courses on project management and team organization. After these steps had been covered, the strategic planning of the network was carried out, producing a significant improvement in the relationship of the participants. The paper will present examples of benefits resulting from such planning and will highlight the limitations so far observed.
1 Fernando Rizzo, Pontifícia Universidade Católica do Rio de Janeiro, Department of Materials Sci... more 1 Fernando Rizzo, Pontifícia Universidade Católica do Rio de Janeiro, Department of Materials Science and Metallurgy, CP38008, Gávea, Rio de Janeiro, RJ, 22453-900, Brazil, rizzo@dcmm.puc-rio.br Abstract The development of cooperative research networks requires the collaboration among partners with different visions about the timing and goals of a research project. In some cases, even competitors are invited to take part in the same initiative, making ground to lack of communication and/or loss of interest in the outcome of the research. During the establishment of the Metal/Mechanics network of the RECOPE program, one large step toward the increase of interaction and collaboration was achieved through one sequence of meetings and short courses on project management and team organization. After these steps had been covered, the strategic planning of the network was carried out, producing a significant improvement in the relationship of the participants. The paper will present exam...
Microporous and Mesoporous Materials, Apr 1, 2008
Thermal expansion of re-hydrated, Al-containing HZSM-5 was studied by different diffraction techn... more Thermal expansion of re-hydrated, Al-containing HZSM-5 was studied by different diffraction techniques, as well as, through thermogravimetry. It is concluded that the nature of the remarkable shift of thermal expansion properties, that occurs in air, between 350°C and 400°C, where the coefficient of thermal expansion changes from positive to negative is due to dehydration of HZSM-5 and not due to dealumination. The intrinsic thermal expansion properties of dehydrated HZSM-5 are observed in the second cycle of neutron diffraction experiments performed in vacuum ($10 À5 Torr). Near zero thermal expansion was observed in the temperature interval between 100°C and 400°C. These intrinsic thermal properties were rationalized in terms of the rigid unit mode model.
Oxidation of Metals, Jun 1, 1995
The oxidation of two Co-Nb alloys containing 15 and 30 wt.% Nb has been studied at 600–800° C in ... more The oxidation of two Co-Nb alloys containing 15 and 30 wt.% Nb has been studied at 600–800° C in H2-CO2 mixtures providing an oxygen pressure of 10-24 atm at 600°C and 10-20 atm at 700 and 800°C, below the dissociation pressure of cobalt oxide. At 600 and 700°C both alloys showed only a region of internal oxidation composed, of a
Materials Science and Engineering: A, 2015
The purpose of this paper is to reveal the dominant factors affecting tensile fracture under a hy... more The purpose of this paper is to reveal the dominant factors affecting tensile fracture under a hydrogen gas atmosphere. Tensile tests were conducted in hydrogen gas with circumferentially-notched specimens of a commercial tempered martensitic steel. Two specimens were exposed to hydrogen gas for 48 h before tensile testing; the other two specimens were not pre-charged. Longitudinal cracks along the loading direction and a transverse crack perpendicular to the loading direction were observed on a cross section of the non-charged specimen, but there was only one small crack on a cross section of the precharged specimen. Electron back scatter diffraction, energy dispersive X-ray spectrometry and finite element method analyses were applied to clarify the relationships among the longitudinal crack, Mn segregation, microstructures of martensitic steel and hydrogen. As a result, it has been demonstrated that Mn segregation and MnS promote hydrogen-assisted cracking in the tempered martensitic steel, causing the longitudinal cracking which is a mechanically non-preferential direction in homogeneous situations. More specifically, we have shown that the role of the Mn segregation is to promote the hydrogen-enhanced decohesion effect (HEDE), which is particularly important for crack propagation in the present case. These considerations indicate that the presence of Mn is crucially important for hydrogen-assisted cracking associated with hydrogen-enhanced localized plasticity (HELP) as well as HEDE.
Journal of Materials Research and Technology, 2021
Soldagem & Inspeção (Impresso), 2010
Com o objetivo de fornecer subsídios para a seleção de consumíveis para a soldagem molhada foram ... more Com o objetivo de fornecer subsídios para a seleção de consumíveis para a soldagem molhada foram determinadas algumas propriedades do metal de solda a partir de juntas soldadas em água doce com eletrodos revestidos comerciais específicos para este fim. As soldas foram realizadas em tanque a 0,5m de profundidade por dispositivo de soldagem por gravidade. Foram levantados dados que auxiliem a eleger os consumíveis de melhor desempenho para serem testados em maiores profundidades. Foram realizados os seguintes testes e avaliações: caracterização microestrutural, análise e quantificação das inclusões, composição química do metal de solda, dureza Vickers, hidrogênio difusível e avaliação da soldabilidade. Os resultados obtidos permitem classificar os consumíveis testados em dois grupos com características bem distintas. No primeiro grupo está o único eletrodo do tipo oxidante e no segundo grupo estão os quatro eletrodos do tipo rutílico testados. Quanto às propriedades mecânicas e às car...
JOM, 2017
The path of society evolution has long been associated with a growing demand for natural resource... more The path of society evolution has long been associated with a growing demand for natural resources and continuous environmental degradation. During the last decades, this pace has accelerated considerably, despite the general concern with the legacy being left for the next generations. Looking ahead, the predicted growth of the world population, and the improvement of life conditions in most regions, point to an increasing demand for energy generation, resulting in additional pressure on the Earth’s sustainability. Materials have had a key role in decreasing the use of natural resources, by either improving efficiency of existing technologies or enabling the development of radical new ones. The greenhouse effect (CO2 emissions) and the energy crisis are global challenges that can benefit from the development of new materials for the successful implementation of promising technologies and for the imperative replacement of fossil fuels by renewable sources.
Soldagem & Inspeção, 2013
A técnica de soldagem subaquática molhada com eletrodos revestidos apresenta um crescente potenci... more A técnica de soldagem subaquática molhada com eletrodos revestidos apresenta um crescente potencial de aplicação para reparos submarinos em elementos estruturais de unidades flutuantes de produção de petróleo (profundidade até 20 m). Porém, ela apresenta problemas tais como o maior risco de fissuração a frio e de formação acentuada de porosidade. O presente trabalho tem como objetivo melhorar a resistência mecânica do metal de solda de um eletrodo experimental do tipo oxi-rutílico. Foram estudadas as influências de adições de Mo (até 0,4% no metal de solda) na microestrutura e em propriedades mecânicas. As soldas foram realizadas em simulador de soldagem subaquática em profundidade equivalente de 10m utilizando um sistema de soldagem por gravidade. As análises das micrografias mostrou que o aumento do teor de Mo no metal de solda diminui significantemente o tamanho médio de grão da região reaquecida de grãos finos. O aumento do teor de Mo no metal de solda resultou, ainda, em aument...
Tecnologia em Metalurgia e Materiais, 2006
Tecnologia em Metalurgia e Materiais, 2005
Tecnologia em Metalurgia e Materiais, 2004
Tecnologia em Metalurgia e Materiais, 2007
Tecnologia em Metalurgia e Materiais, 2004
The development of cooperative research networks requires the collaboration among partners with d... more The development of cooperative research networks requires the collaboration among partners with different visions about the timing and goals of a research project. In some cases, even competitors are invited to take part in the same initiative, making ground to lack of communication and/or loss of interest in the outcome of the research. During the establishment of the Metal/Mechanics network of the RECOPE program, one large step toward the increase of interaction and collaboration was achieved through one sequence of meetings and short courses on project management and team organization. After these steps had been covered, the strategic planning of the network was carried out, producing a significant improvement in the relationship of the participants. The paper will present examples of benefits resulting from such planning and will highlight the limitations so far observed.
1 Fernando Rizzo, Pontifícia Universidade Católica do Rio de Janeiro, Department of Materials Sci... more 1 Fernando Rizzo, Pontifícia Universidade Católica do Rio de Janeiro, Department of Materials Science and Metallurgy, CP38008, Gávea, Rio de Janeiro, RJ, 22453-900, Brazil, rizzo@dcmm.puc-rio.br Abstract The development of cooperative research networks requires the collaboration among partners with different visions about the timing and goals of a research project. In some cases, even competitors are invited to take part in the same initiative, making ground to lack of communication and/or loss of interest in the outcome of the research. During the establishment of the Metal/Mechanics network of the RECOPE program, one large step toward the increase of interaction and collaboration was achieved through one sequence of meetings and short courses on project management and team organization. After these steps had been covered, the strategic planning of the network was carried out, producing a significant improvement in the relationship of the participants. The paper will present exam...
Microporous and Mesoporous Materials, Apr 1, 2008
Thermal expansion of re-hydrated, Al-containing HZSM-5 was studied by different diffraction techn... more Thermal expansion of re-hydrated, Al-containing HZSM-5 was studied by different diffraction techniques, as well as, through thermogravimetry. It is concluded that the nature of the remarkable shift of thermal expansion properties, that occurs in air, between 350°C and 400°C, where the coefficient of thermal expansion changes from positive to negative is due to dehydration of HZSM-5 and not due to dealumination. The intrinsic thermal expansion properties of dehydrated HZSM-5 are observed in the second cycle of neutron diffraction experiments performed in vacuum ($10 À5 Torr). Near zero thermal expansion was observed in the temperature interval between 100°C and 400°C. These intrinsic thermal properties were rationalized in terms of the rigid unit mode model.
Oxidation of Metals, Jun 1, 1995
The oxidation of two Co-Nb alloys containing 15 and 30 wt.% Nb has been studied at 600–800° C in ... more The oxidation of two Co-Nb alloys containing 15 and 30 wt.% Nb has been studied at 600–800° C in H2-CO2 mixtures providing an oxygen pressure of 10-24 atm at 600°C and 10-20 atm at 700 and 800°C, below the dissociation pressure of cobalt oxide. At 600 and 700°C both alloys showed only a region of internal oxidation composed, of a