The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
H E Troiani - One of the best experts on this subject based on the ideXlab platform.
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primordial hexagonal phase formation during the bcc Dezincification of the β cu zn single crystalline surface matrix instabilization and transformation path
Journal of Alloys and Compounds, 2009Co-Authors: A Baruj, M Granada, Arneodo P Larochette, S Sommadossi, H E TroianiAbstract:Abstract Subjecting Cu–Zn samples to annealing under dynamical vacuum produces the evaporation of Zn, a process known as Dezincification. Here, we study the phase transitions related to Dezincification of Cu–48 at.% Zn (bcc, Beta phase) single crystalline surfaces with residual stresses due to mechanical polishing. In order to identify different steps in the Dezincification process of these deformed samples we apply a combination of in situ optical microscopy and transmission electron microscopy (TEM) observations. The former allows us to control and stop the Dezincification process at a specific stage of evolution while the latter allows relating surface features with structure and composition changes. Due to Dezincification, the formation of an on average 4H hexagonal phase and the fcc equilibrium phase take place. TEM observations show that the bcc to 4H phase transformation occurs by a mechanism of nucleation and growth. In particular, we show evidence of the mechanism of embryo formation for the first time. During the subsequent growth process, the coalescence of transformed zones defines regions in the micron range which after subsequent prolonged Dezincification transform to the final fcc equilibrium structure. These experiments provide an insight on the reason for the formation of the non-equilibrium hexagonal phase during the Dezincification of electropolished (non-deformed) samples. The new experimental results evidence the heterogeneous character of the Dezincification.
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surface phase transformation induced by the Dezincification of a beta cu zn alloy on highly deformed systems
Applied Surface Science, 2007Co-Authors: A Baruj, Arneodo P Larochette, S Sommadossi, H E TroianiAbstract:Abstract When Cu–Zn alloys are annealed under dynamical vacuum the Zn component evaporates. The process is called Dezincification. This paper presents the results of the Dezincification of highly mechanically deformed surfaces of samples initially in the beta (bcc) phase by a combination of in situ optical microscopy observations together with TEM measurements. It is shown that grinding lines remaining from the sample preparation process act as nucleation centers for the alpha (fcc) phase. Under this surface preparation conditions the new fcc phase nucleates with a different geometry than the one reported in previous papers in which surfaces were finished by electropolishing. In the present case, we observe individual fcc precipitates with a well defined geometry. The typical size of precipitates is in the micron range, and depends on the Dezincification parameters: final temperature, Dezincification time and prior surface preparation. TEM observations show that the fcc precipitates contain a large density of defects, mainly dislocations and twin boundaries.
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in situ optical microscopy study of a phase transformation induced by the Dezincification of beta cu zn
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: H E Troiani, A BarujAbstract:Abstract The formation of the alpha fcc phase during the Dezincification of beta Cu–Zn was in situ observed. The transformation temperature (470 °C) was close to the minimum temperature at which the transformation could be detected in previous works. The reason for choosing this temperature was that in this way the transformation proceeds sufficiently slowly, making it possible to observe clearly the nucleation stage and the growing process at the surface of the sample. The progress of the Dezincification experiment was recorded as a function of time allowing to follow the growing process of fcc needles. The experiments indicated that the formation of the fcc precipitates takes place by a heterogeneous mechanism.
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In situ optical microscopy study of a phase transformation induced by the Dezincification of beta Cu–Zn
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: H E Troiani, Alberto BarujAbstract:Abstract The formation of the alpha fcc phase during the Dezincification of beta Cu–Zn was in situ observed. The transformation temperature (470 °C) was close to the minimum temperature at which the transformation could be detected in previous works. The reason for choosing this temperature was that in this way the transformation proceeds sufficiently slowly, making it possible to observe clearly the nucleation stage and the growing process at the surface of the sample. The progress of the Dezincification experiment was recorded as a function of time allowing to follow the growing process of fcc needles. The experiments indicated that the formation of the fcc precipitates takes place by a heterogeneous mechanism.
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pore formation during Dezincification of zn based alloys
Applied Surface Science, 1999Co-Authors: M N Kuperman, H E TroianiAbstract:Abstract We examine a model for the formation of pores during Dezincification of Zn-based, which is based on a reaction–diffusion equation including flux terms. The pores are treated as a condensed phase for vacancies. We obtain numerical results for the velocity of pore growth and its dependence on temperature, and have analyzed the behaviour of the system at different temperatures both analytical and experimentally. Our results show good agreement with experiment.
A Baruj - One of the best experts on this subject based on the ideXlab platform.
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primordial hexagonal phase formation during the bcc Dezincification of the β cu zn single crystalline surface matrix instabilization and transformation path
Journal of Alloys and Compounds, 2009Co-Authors: A Baruj, M Granada, Arneodo P Larochette, S Sommadossi, H E TroianiAbstract:Abstract Subjecting Cu–Zn samples to annealing under dynamical vacuum produces the evaporation of Zn, a process known as Dezincification. Here, we study the phase transitions related to Dezincification of Cu–48 at.% Zn (bcc, Beta phase) single crystalline surfaces with residual stresses due to mechanical polishing. In order to identify different steps in the Dezincification process of these deformed samples we apply a combination of in situ optical microscopy and transmission electron microscopy (TEM) observations. The former allows us to control and stop the Dezincification process at a specific stage of evolution while the latter allows relating surface features with structure and composition changes. Due to Dezincification, the formation of an on average 4H hexagonal phase and the fcc equilibrium phase take place. TEM observations show that the bcc to 4H phase transformation occurs by a mechanism of nucleation and growth. In particular, we show evidence of the mechanism of embryo formation for the first time. During the subsequent growth process, the coalescence of transformed zones defines regions in the micron range which after subsequent prolonged Dezincification transform to the final fcc equilibrium structure. These experiments provide an insight on the reason for the formation of the non-equilibrium hexagonal phase during the Dezincification of electropolished (non-deformed) samples. The new experimental results evidence the heterogeneous character of the Dezincification.
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surface phase transformation induced by the Dezincification of a beta cu zn alloy on highly deformed systems
Applied Surface Science, 2007Co-Authors: A Baruj, Arneodo P Larochette, S Sommadossi, H E TroianiAbstract:Abstract When Cu–Zn alloys are annealed under dynamical vacuum the Zn component evaporates. The process is called Dezincification. This paper presents the results of the Dezincification of highly mechanically deformed surfaces of samples initially in the beta (bcc) phase by a combination of in situ optical microscopy observations together with TEM measurements. It is shown that grinding lines remaining from the sample preparation process act as nucleation centers for the alpha (fcc) phase. Under this surface preparation conditions the new fcc phase nucleates with a different geometry than the one reported in previous papers in which surfaces were finished by electropolishing. In the present case, we observe individual fcc precipitates with a well defined geometry. The typical size of precipitates is in the micron range, and depends on the Dezincification parameters: final temperature, Dezincification time and prior surface preparation. TEM observations show that the fcc precipitates contain a large density of defects, mainly dislocations and twin boundaries.
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in situ optical microscopy study of a phase transformation induced by the Dezincification of beta cu zn
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: H E Troiani, A BarujAbstract:Abstract The formation of the alpha fcc phase during the Dezincification of beta Cu–Zn was in situ observed. The transformation temperature (470 °C) was close to the minimum temperature at which the transformation could be detected in previous works. The reason for choosing this temperature was that in this way the transformation proceeds sufficiently slowly, making it possible to observe clearly the nucleation stage and the growing process at the surface of the sample. The progress of the Dezincification experiment was recorded as a function of time allowing to follow the growing process of fcc needles. The experiments indicated that the formation of the fcc precipitates takes place by a heterogeneous mechanism.
Lijie Qiao - One of the best experts on this subject based on the ideXlab platform.
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correspondence between hydrogen enhancing Dezincification layer induced stress and susceptibility to scc of brass
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Hui Li, Lijie QiaoAbstract:Dezincification layer formed during corrosion or stress corrosion cracking (SCC) of brass in the ammonia solution could induce an additive stress. The effect of hydrogen on the Dezincification layer-induced stress and the susceptibility to SCC were studied. The Dezincification layer-induced stress was measured using the deflection method and the flow stress differential method. The susceptibility to SCC was measured using a slow strain rate test. Results showed that both the Dezincification layer-induced stress and the susceptibility to SCC increased with increasing hydrogen concentration, and the hydrogen concentration dependence of the susceptibility to SCC was in a good agreement with that of the Dezincification layer-induced stress. Hydrogen in brass facilitates the selective dissolution of Zn in the ammonia solution, and then enhances the Dezincification layer-induced stress.
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stress corrosion cracking relation with Dezincification layer induced stress
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2001Co-Authors: Lijie QiaoAbstract:Brass foil with a protective layer formed on one side was deflected during corrosion in an ammonia solution under various applied potentials, and then corrosion-induced stress generated at brass/Dezincification layer under different potentials could be measured. At the same time, susceptibility to stress corrosion cracking (SCC) of brass in the ammonia solution under various applied potentials was measured by using a single-edge notched specimen. At open-circuit potential, both corrosion-induced tensile stress and susceptibility to SCC (I σ) had a maximum value. Both tensile stress σ p and susceptibility I σ decreased slightly with decreasing potential under anodic polarization, but reduced steeply with a decrease in potential under cathodic polarization. At the cathodic potential of − 500 mVSCE, corrosioninduced stress became compressive because of the copper-plating layer; correspondingly, susceptibility to SCC was zero. Therefore, the variation of SCC susceptibility with potential is consistent with that of the corrosion-induced additive stress.
Hong Lu - One of the best experts on this subject based on the ideXlab platform.
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determination of tensile stress induced by Dezincification layer during corrosion for brass
Corrosion Science, 1998Co-Authors: Hong LuAbstract:The brass foil with a protective layer formed on one side was deflected during original corrosion in 1 mol⧹L NH4OH+5 g⧹LCuCl2 solution. This was due to corrosion-induced tensile stress developed in the Dezincification layer of the sample. The additive tensile stress grew gradually, and reached a steady value of about 24.4 MPa, i.e., 20% of the yield stress of brass.
Arneodo P Larochette - One of the best experts on this subject based on the ideXlab platform.
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primordial hexagonal phase formation during the bcc Dezincification of the β cu zn single crystalline surface matrix instabilization and transformation path
Journal of Alloys and Compounds, 2009Co-Authors: A Baruj, M Granada, Arneodo P Larochette, S Sommadossi, H E TroianiAbstract:Abstract Subjecting Cu–Zn samples to annealing under dynamical vacuum produces the evaporation of Zn, a process known as Dezincification. Here, we study the phase transitions related to Dezincification of Cu–48 at.% Zn (bcc, Beta phase) single crystalline surfaces with residual stresses due to mechanical polishing. In order to identify different steps in the Dezincification process of these deformed samples we apply a combination of in situ optical microscopy and transmission electron microscopy (TEM) observations. The former allows us to control and stop the Dezincification process at a specific stage of evolution while the latter allows relating surface features with structure and composition changes. Due to Dezincification, the formation of an on average 4H hexagonal phase and the fcc equilibrium phase take place. TEM observations show that the bcc to 4H phase transformation occurs by a mechanism of nucleation and growth. In particular, we show evidence of the mechanism of embryo formation for the first time. During the subsequent growth process, the coalescence of transformed zones defines regions in the micron range which after subsequent prolonged Dezincification transform to the final fcc equilibrium structure. These experiments provide an insight on the reason for the formation of the non-equilibrium hexagonal phase during the Dezincification of electropolished (non-deformed) samples. The new experimental results evidence the heterogeneous character of the Dezincification.
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surface phase transformation induced by the Dezincification of a beta cu zn alloy on highly deformed systems
Applied Surface Science, 2007Co-Authors: A Baruj, Arneodo P Larochette, S Sommadossi, H E TroianiAbstract:Abstract When Cu–Zn alloys are annealed under dynamical vacuum the Zn component evaporates. The process is called Dezincification. This paper presents the results of the Dezincification of highly mechanically deformed surfaces of samples initially in the beta (bcc) phase by a combination of in situ optical microscopy observations together with TEM measurements. It is shown that grinding lines remaining from the sample preparation process act as nucleation centers for the alpha (fcc) phase. Under this surface preparation conditions the new fcc phase nucleates with a different geometry than the one reported in previous papers in which surfaces were finished by electropolishing. In the present case, we observe individual fcc precipitates with a well defined geometry. The typical size of precipitates is in the micron range, and depends on the Dezincification parameters: final temperature, Dezincification time and prior surface preparation. TEM observations show that the fcc precipitates contain a large density of defects, mainly dislocations and twin boundaries.