The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
R.a.g. Silva - One of the best experts on this subject based on the ideXlab platform.
-
Effects of Co and Zr additions on the thermal behavior of the Cu_81Al_19 alloy
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: R. D. A. Pinto, L. D. R. Ferreira, R.a.g. SilvaAbstract:The thermal behavior of the annealed Cu_81Al_19 alloy with Co and Zr additions was investigated using differential thermal analysis, differential scanning calorimetry, electrical resistivity measurements, optical microscopy, scanning electron microscopy, Vickers microhardness, and X-ray diffractometry. The results showed that the Co addition slightly increased the critical temperatures of melting and solidification of the Cu_81Al_19 alloy, suppressed the Eutectoid Reaction and the β phase ordering, and introduced a new route for the α _2 phase disordering. A mechanism to this phenomenon is suggested in the present work. On the other hand, the Zr addition did not significantly alter the critical temperatures of melting and solidification of the Cu_81Al_19 alloy, decreased the intensity of the Eutectoid Reaction, and increased the α _2 phase disordering rate and the β phase decomposition. Besides that, it introduced a new thermal event at higher temperatures, related to the dissolution of precipitates with Al. Both Zr and Co additions increased the electrical resistivity and the microhardness of the Cu_81Al_19 alloy due to the precipitation of intermetallic compounds.
-
Effects of Co and Zr additions on the thermal behavior of the Cu 81 Al 19 alloy
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: R. D. A. Pinto, L. D. R. Ferreira, R.a.g. SilvaAbstract:The thermal behavior of the annealed Cu81Al19 alloy with Co and Zr additions was investigated using differential thermal analysis, differential scanning calorimetry, electrical resistivity measurements, optical microscopy, scanning electron microscopy, Vickers microhardness, and X-ray diffractometry. The results showed that the Co addition slightly increased the critical temperatures of melting and solidification of the Cu81Al19 alloy, suppressed the Eutectoid Reaction and the β phase ordering, and introduced a new route for the α2 phase disordering. A mechanism to this phenomenon is suggested in the present work. On the other hand, the Zr addition did not significantly alter the critical temperatures of melting and solidification of the Cu81Al19 alloy, decreased the intensity of the Eutectoid Reaction, and increased the α2 phase disordering rate and the β phase decomposition. Besides that, it introduced a new thermal event at higher temperatures, related to the dissolution of precipitates with Al. Both Zr and Co additions increased the electrical resistivity and the microhardness of the Cu81Al19 alloy due to the precipitation of intermetallic compounds.
-
Activation energy for the reverse Eutectoid Reaction in hypo-Eutectoid Cu–Al alloys
Thermochimica Acta, 2012Co-Authors: A. T. Adorno, T. M. Carvalho, A. G. Magdalena, C.m.a. Dos Santos, R.a.g. SilvaAbstract:Abstract The values of the activation energy for the reverse Eutectoid Reaction (α + γ 1 ) → β in the Cu–9 wt.%Al, Cu–10 wt.%Al and Cu–11 wt.%Al alloys were obtained using nonisothermal methods and considering two different Reaction paths, one starting from annealed alloys and other from quenched alloys. The results showed that the activation energy for the Reaction changes with Al concentration and strongly depends on the Reaction path. The conversion dependence of the activation energy indicates a complex process comprising consecutive Reactions which may be related with the dissolution of the pearlitic phase prior to the β phase formation.
-
Influence of Ag additions on the activation energy for the reverse Eutectoid Reaction in Cu–Al alloys
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: T. M. Carvalho, A. T. Adorno, A. G. Magdalena, R.a.g. SilvaAbstract:The Eutectoid transformation may be defined as a solid-state diffusion-controlled decomposition process of a high-temperature phase into a two-phase lamellar aggregate behind a migrating boundary on cooling below the Eutectoid temperature. In substitutional solid solutions, the Eutectoid Reaction involves diffusion of the solute atoms either through the matrix or along the boundaries or ledges. The effect of Ag on the non-isothermal kinetics of the reverse Eutectoid Reaction in the Cu–9 mass%Al, Cu–10 mass%Al, and Cu–11 mass%Al alloys were studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The activation energy for this Reaction was obtained using the Kissinger and Ozawa methods. The results indicated that Ag additions to Cu–Al alloys interfere on the reverse Eutectoid Reaction, increasing the activation energy values for the Cu–9 mass%Al and Cu–10 mass%Al alloys and decreasing these values for the Cu–11 mass%Al alloy for additions up to 6 mass%Ag. The changes in the activation energy were attributed to changes in the Reaction solute and in Ag solubility due to the increase in Al content.
-
β Phase transformations in the Cu–11mass%Al alloy with Ag additions
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: A. G. Magdalena, A. T. Adorno, T. M. Carvalho, R.a.g. SilvaAbstract:In the Cu–Al system, due to the sluggishness of the β ↔ (α + γ_1) Eutectoid Reaction, the β phase can be retained metastably. During quenching, metastable β alloys undergo a martensitic transformation to a β′ phase at Al low content. The ordering Reaction β ↔ β_1 precedes the martensitic transformation. The influence of Ag additions on the Reactions containing the β phase in the Cu–11mass%Al alloy was studied using differential scanning calorimetry and in situ X-ray diffractometry. The results indicated that, on cooling, two Reactions are occurring in the same temperature range, the β → (α + γ_1) decomposition Reaction and the β → β_1 Reaction, with different Reaction mechanisms (diffusive for the former and ordering for the latter) and, consequently, with different Reaction rates. For lower cooling rates, the dominant is the decomposition Reaction and for higher cooling rates the ordering Reaction prevails. On heating, the (α + γ_1) → β reverse Eutectoid Reaction occurs with a resulting β phase saturated with α. The increase of Ag concentration retards the β → (α + γ_1) decomposition Reaction and the β → β_1 ordering Reaction, which occurs in the same temperature range, becomes the predominant process.
R. D. A. Pinto - One of the best experts on this subject based on the ideXlab platform.
-
Effects of Co and Zr additions on the thermal behavior of the Cu_81Al_19 alloy
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: R. D. A. Pinto, L. D. R. Ferreira, R.a.g. SilvaAbstract:The thermal behavior of the annealed Cu_81Al_19 alloy with Co and Zr additions was investigated using differential thermal analysis, differential scanning calorimetry, electrical resistivity measurements, optical microscopy, scanning electron microscopy, Vickers microhardness, and X-ray diffractometry. The results showed that the Co addition slightly increased the critical temperatures of melting and solidification of the Cu_81Al_19 alloy, suppressed the Eutectoid Reaction and the β phase ordering, and introduced a new route for the α _2 phase disordering. A mechanism to this phenomenon is suggested in the present work. On the other hand, the Zr addition did not significantly alter the critical temperatures of melting and solidification of the Cu_81Al_19 alloy, decreased the intensity of the Eutectoid Reaction, and increased the α _2 phase disordering rate and the β phase decomposition. Besides that, it introduced a new thermal event at higher temperatures, related to the dissolution of precipitates with Al. Both Zr and Co additions increased the electrical resistivity and the microhardness of the Cu_81Al_19 alloy due to the precipitation of intermetallic compounds.
-
Effects of Co and Zr additions on the thermal behavior of the Cu 81 Al 19 alloy
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: R. D. A. Pinto, L. D. R. Ferreira, R.a.g. SilvaAbstract:The thermal behavior of the annealed Cu81Al19 alloy with Co and Zr additions was investigated using differential thermal analysis, differential scanning calorimetry, electrical resistivity measurements, optical microscopy, scanning electron microscopy, Vickers microhardness, and X-ray diffractometry. The results showed that the Co addition slightly increased the critical temperatures of melting and solidification of the Cu81Al19 alloy, suppressed the Eutectoid Reaction and the β phase ordering, and introduced a new route for the α2 phase disordering. A mechanism to this phenomenon is suggested in the present work. On the other hand, the Zr addition did not significantly alter the critical temperatures of melting and solidification of the Cu81Al19 alloy, decreased the intensity of the Eutectoid Reaction, and increased the α2 phase disordering rate and the β phase decomposition. Besides that, it introduced a new thermal event at higher temperatures, related to the dissolution of precipitates with Al. Both Zr and Co additions increased the electrical resistivity and the microhardness of the Cu81Al19 alloy due to the precipitation of intermetallic compounds.
T. M. Carvalho - One of the best experts on this subject based on the ideXlab platform.
-
Activation energy for the reverse Eutectoid Reaction in hypo-Eutectoid Cu–Al alloys
Thermochimica Acta, 2012Co-Authors: A. T. Adorno, T. M. Carvalho, A. G. Magdalena, C.m.a. Dos Santos, R.a.g. SilvaAbstract:Abstract The values of the activation energy for the reverse Eutectoid Reaction (α + γ 1 ) → β in the Cu–9 wt.%Al, Cu–10 wt.%Al and Cu–11 wt.%Al alloys were obtained using nonisothermal methods and considering two different Reaction paths, one starting from annealed alloys and other from quenched alloys. The results showed that the activation energy for the Reaction changes with Al concentration and strongly depends on the Reaction path. The conversion dependence of the activation energy indicates a complex process comprising consecutive Reactions which may be related with the dissolution of the pearlitic phase prior to the β phase formation.
-
Influence of Ag additions on the activation energy for the reverse Eutectoid Reaction in Cu–Al alloys
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: T. M. Carvalho, A. T. Adorno, A. G. Magdalena, R.a.g. SilvaAbstract:The Eutectoid transformation may be defined as a solid-state diffusion-controlled decomposition process of a high-temperature phase into a two-phase lamellar aggregate behind a migrating boundary on cooling below the Eutectoid temperature. In substitutional solid solutions, the Eutectoid Reaction involves diffusion of the solute atoms either through the matrix or along the boundaries or ledges. The effect of Ag on the non-isothermal kinetics of the reverse Eutectoid Reaction in the Cu–9 mass%Al, Cu–10 mass%Al, and Cu–11 mass%Al alloys were studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The activation energy for this Reaction was obtained using the Kissinger and Ozawa methods. The results indicated that Ag additions to Cu–Al alloys interfere on the reverse Eutectoid Reaction, increasing the activation energy values for the Cu–9 mass%Al and Cu–10 mass%Al alloys and decreasing these values for the Cu–11 mass%Al alloy for additions up to 6 mass%Ag. The changes in the activation energy were attributed to changes in the Reaction solute and in Ag solubility due to the increase in Al content.
-
β Phase transformations in the Cu–11mass%Al alloy with Ag additions
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: A. G. Magdalena, A. T. Adorno, T. M. Carvalho, R.a.g. SilvaAbstract:In the Cu–Al system, due to the sluggishness of the β ↔ (α + γ_1) Eutectoid Reaction, the β phase can be retained metastably. During quenching, metastable β alloys undergo a martensitic transformation to a β′ phase at Al low content. The ordering Reaction β ↔ β_1 precedes the martensitic transformation. The influence of Ag additions on the Reactions containing the β phase in the Cu–11mass%Al alloy was studied using differential scanning calorimetry and in situ X-ray diffractometry. The results indicated that, on cooling, two Reactions are occurring in the same temperature range, the β → (α + γ_1) decomposition Reaction and the β → β_1 Reaction, with different Reaction mechanisms (diffusive for the former and ordering for the latter) and, consequently, with different Reaction rates. For lower cooling rates, the dominant is the decomposition Reaction and for higher cooling rates the ordering Reaction prevails. On heating, the (α + γ_1) → β reverse Eutectoid Reaction occurs with a resulting β phase saturated with α. The increase of Ag concentration retards the β → (α + γ_1) decomposition Reaction and the β → β_1 ordering Reaction, which occurs in the same temperature range, becomes the predominant process.
A. T. Adorno - One of the best experts on this subject based on the ideXlab platform.
-
Activation energy for the reverse Eutectoid Reaction in hypo-Eutectoid Cu–Al alloys
Thermochimica Acta, 2012Co-Authors: A. T. Adorno, T. M. Carvalho, A. G. Magdalena, C.m.a. Dos Santos, R.a.g. SilvaAbstract:Abstract The values of the activation energy for the reverse Eutectoid Reaction (α + γ 1 ) → β in the Cu–9 wt.%Al, Cu–10 wt.%Al and Cu–11 wt.%Al alloys were obtained using nonisothermal methods and considering two different Reaction paths, one starting from annealed alloys and other from quenched alloys. The results showed that the activation energy for the Reaction changes with Al concentration and strongly depends on the Reaction path. The conversion dependence of the activation energy indicates a complex process comprising consecutive Reactions which may be related with the dissolution of the pearlitic phase prior to the β phase formation.
-
Influence of Ag additions on the activation energy for the reverse Eutectoid Reaction in Cu–Al alloys
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: T. M. Carvalho, A. T. Adorno, A. G. Magdalena, R.a.g. SilvaAbstract:The Eutectoid transformation may be defined as a solid-state diffusion-controlled decomposition process of a high-temperature phase into a two-phase lamellar aggregate behind a migrating boundary on cooling below the Eutectoid temperature. In substitutional solid solutions, the Eutectoid Reaction involves diffusion of the solute atoms either through the matrix or along the boundaries or ledges. The effect of Ag on the non-isothermal kinetics of the reverse Eutectoid Reaction in the Cu–9 mass%Al, Cu–10 mass%Al, and Cu–11 mass%Al alloys were studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The activation energy for this Reaction was obtained using the Kissinger and Ozawa methods. The results indicated that Ag additions to Cu–Al alloys interfere on the reverse Eutectoid Reaction, increasing the activation energy values for the Cu–9 mass%Al and Cu–10 mass%Al alloys and decreasing these values for the Cu–11 mass%Al alloy for additions up to 6 mass%Ag. The changes in the activation energy were attributed to changes in the Reaction solute and in Ag solubility due to the increase in Al content.
-
β Phase transformations in the Cu–11mass%Al alloy with Ag additions
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: A. G. Magdalena, A. T. Adorno, T. M. Carvalho, R.a.g. SilvaAbstract:In the Cu–Al system, due to the sluggishness of the β ↔ (α + γ_1) Eutectoid Reaction, the β phase can be retained metastably. During quenching, metastable β alloys undergo a martensitic transformation to a β′ phase at Al low content. The ordering Reaction β ↔ β_1 precedes the martensitic transformation. The influence of Ag additions on the Reactions containing the β phase in the Cu–11mass%Al alloy was studied using differential scanning calorimetry and in situ X-ray diffractometry. The results indicated that, on cooling, two Reactions are occurring in the same temperature range, the β → (α + γ_1) decomposition Reaction and the β → β_1 Reaction, with different Reaction mechanisms (diffusive for the former and ordering for the latter) and, consequently, with different Reaction rates. For lower cooling rates, the dominant is the decomposition Reaction and for higher cooling rates the ordering Reaction prevails. On heating, the (α + γ_1) → β reverse Eutectoid Reaction occurs with a resulting β phase saturated with α. The increase of Ag concentration retards the β → (α + γ_1) decomposition Reaction and the β → β_1 ordering Reaction, which occurs in the same temperature range, becomes the predominant process.
A. G. Magdalena - One of the best experts on this subject based on the ideXlab platform.
-
Activation energy for the reverse Eutectoid Reaction in hypo-Eutectoid Cu–Al alloys
Thermochimica Acta, 2012Co-Authors: A. T. Adorno, T. M. Carvalho, A. G. Magdalena, C.m.a. Dos Santos, R.a.g. SilvaAbstract:Abstract The values of the activation energy for the reverse Eutectoid Reaction (α + γ 1 ) → β in the Cu–9 wt.%Al, Cu–10 wt.%Al and Cu–11 wt.%Al alloys were obtained using nonisothermal methods and considering two different Reaction paths, one starting from annealed alloys and other from quenched alloys. The results showed that the activation energy for the Reaction changes with Al concentration and strongly depends on the Reaction path. The conversion dependence of the activation energy indicates a complex process comprising consecutive Reactions which may be related with the dissolution of the pearlitic phase prior to the β phase formation.
-
Influence of Ag additions on the activation energy for the reverse Eutectoid Reaction in Cu–Al alloys
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: T. M. Carvalho, A. T. Adorno, A. G. Magdalena, R.a.g. SilvaAbstract:The Eutectoid transformation may be defined as a solid-state diffusion-controlled decomposition process of a high-temperature phase into a two-phase lamellar aggregate behind a migrating boundary on cooling below the Eutectoid temperature. In substitutional solid solutions, the Eutectoid Reaction involves diffusion of the solute atoms either through the matrix or along the boundaries or ledges. The effect of Ag on the non-isothermal kinetics of the reverse Eutectoid Reaction in the Cu–9 mass%Al, Cu–10 mass%Al, and Cu–11 mass%Al alloys were studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The activation energy for this Reaction was obtained using the Kissinger and Ozawa methods. The results indicated that Ag additions to Cu–Al alloys interfere on the reverse Eutectoid Reaction, increasing the activation energy values for the Cu–9 mass%Al and Cu–10 mass%Al alloys and decreasing these values for the Cu–11 mass%Al alloy for additions up to 6 mass%Ag. The changes in the activation energy were attributed to changes in the Reaction solute and in Ag solubility due to the increase in Al content.
-
β Phase transformations in the Cu–11mass%Al alloy with Ag additions
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: A. G. Magdalena, A. T. Adorno, T. M. Carvalho, R.a.g. SilvaAbstract:In the Cu–Al system, due to the sluggishness of the β ↔ (α + γ_1) Eutectoid Reaction, the β phase can be retained metastably. During quenching, metastable β alloys undergo a martensitic transformation to a β′ phase at Al low content. The ordering Reaction β ↔ β_1 precedes the martensitic transformation. The influence of Ag additions on the Reactions containing the β phase in the Cu–11mass%Al alloy was studied using differential scanning calorimetry and in situ X-ray diffractometry. The results indicated that, on cooling, two Reactions are occurring in the same temperature range, the β → (α + γ_1) decomposition Reaction and the β → β_1 Reaction, with different Reaction mechanisms (diffusive for the former and ordering for the latter) and, consequently, with different Reaction rates. For lower cooling rates, the dominant is the decomposition Reaction and for higher cooling rates the ordering Reaction prevails. On heating, the (α + γ_1) → β reverse Eutectoid Reaction occurs with a resulting β phase saturated with α. The increase of Ag concentration retards the β → (α + γ_1) decomposition Reaction and the β → β_1 ordering Reaction, which occurs in the same temperature range, becomes the predominant process.
