The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Wensong Kou - One of the best experts on this subject based on the ideXlab platform.
-
effects of lead ii oxide on processing and properties of low temperature cofirable ni cu zn Ferrite
Journal of the American Ceramic Society, 2004Co-Authors: Jauho Jean, Chenghorng Lee, Wensong KouAbstract:The effects of PbO addition on the densification, microstructure, and properties of low-temperature cofirable Ni-Cu-Zn Ferrite have been investigated. With a small amount of PbO (0.5–2 wt%) present as a dopant in the Ni-Cu-Zn Ferrite, the densification rate and final sintered density are greatly increased, but the activation energy of densification is significantly reduced. These results are attributed to a chemical reaction that occurs at the PbO/Ni-Cu-Zn Ferrite Interface, resulting in a greater amount of liquid phase and good wetting during sintering. However, the above-mentioned interfacial reaction causes segregation of CuO onto the grain boundary and dissolution of PbO into the Ferrite grains, yielding a reduction in initial permeability.
-
Effects of Lead(II) Oxide on Processing and Properties of Low‐Temperature‐Cofirable Ni‐Cu‐Zn Ferrite
Journal of the American Ceramic Society, 2004Co-Authors: Jauho Jean, Chenghorng Lee, Wensong KouAbstract:The effects of PbO addition on the densification, microstructure, and properties of low-temperature cofirable Ni-Cu-Zn Ferrite have been investigated. With a small amount of PbO (0.5–2 wt%) present as a dopant in the Ni-Cu-Zn Ferrite, the densification rate and final sintered density are greatly increased, but the activation energy of densification is significantly reduced. These results are attributed to a chemical reaction that occurs at the PbO/Ni-Cu-Zn Ferrite Interface, resulting in a greater amount of liquid phase and good wetting during sintering. However, the above-mentioned interfacial reaction causes segregation of CuO onto the grain boundary and dissolution of PbO into the Ferrite grains, yielding a reduction in initial permeability.
Jauho Jean - One of the best experts on this subject based on the ideXlab platform.
-
effects of lead ii oxide on processing and properties of low temperature cofirable ni cu zn Ferrite
Journal of the American Ceramic Society, 2004Co-Authors: Jauho Jean, Chenghorng Lee, Wensong KouAbstract:The effects of PbO addition on the densification, microstructure, and properties of low-temperature cofirable Ni-Cu-Zn Ferrite have been investigated. With a small amount of PbO (0.5–2 wt%) present as a dopant in the Ni-Cu-Zn Ferrite, the densification rate and final sintered density are greatly increased, but the activation energy of densification is significantly reduced. These results are attributed to a chemical reaction that occurs at the PbO/Ni-Cu-Zn Ferrite Interface, resulting in a greater amount of liquid phase and good wetting during sintering. However, the above-mentioned interfacial reaction causes segregation of CuO onto the grain boundary and dissolution of PbO into the Ferrite grains, yielding a reduction in initial permeability.
-
Effects of Lead(II) Oxide on Processing and Properties of Low‐Temperature‐Cofirable Ni‐Cu‐Zn Ferrite
Journal of the American Ceramic Society, 2004Co-Authors: Jauho Jean, Chenghorng Lee, Wensong KouAbstract:The effects of PbO addition on the densification, microstructure, and properties of low-temperature cofirable Ni-Cu-Zn Ferrite have been investigated. With a small amount of PbO (0.5–2 wt%) present as a dopant in the Ni-Cu-Zn Ferrite, the densification rate and final sintered density are greatly increased, but the activation energy of densification is significantly reduced. These results are attributed to a chemical reaction that occurs at the PbO/Ni-Cu-Zn Ferrite Interface, resulting in a greater amount of liquid phase and good wetting during sintering. However, the above-mentioned interfacial reaction causes segregation of CuO onto the grain boundary and dissolution of PbO into the Ferrite grains, yielding a reduction in initial permeability.
Varvara G. Kouznetsova - One of the best experts on this subject based on the ideXlab platform.
-
revisiting the martensite Ferrite Interface damage initiation mechanism the key role of substructure boundary sliding
Acta Materialia, 2021Co-Authors: Lei Liu, Francesco Maresca, Johan P.m. Hoefnagels, Tijmen Vermeij, Marc G. D. Geers, Varvara G. KouznetsovaAbstract:Abstract Martensite/Ferrite (M/F) Interface damage plays a critical role in controlling failure of dual-phase (DP) steels and is commonly understood to originate from the large phase contrast between martensite and Ferrite. This however conflicts with a few, recent observations, showing that considerable M/F Interface damage initiation is often accompanied by apparent martensite island plasticity and weak M/F strain partitioning. In fact, martensite has a complex hierarchical structure which induces a strongly heterogeneous and orientation-dependent plastic response. Depending on the local stress state, (lath) martensite is presumed to be hard to deform based on common understanding. However, when favourably oriented, substructure boundary sliding can be triggered at a resolved shear stress which is comparable to that of Ferrite. Moreover, careful measurements of the M/F Interface structure indicate the occurrence of sharp martensite wedges protruding into the Ferrite and clear steps in correspondence with lath boundaries, constituting a jagged M/F interfacial morphology that may have a large effect on the M/F Interface behaviour. By taking into account the substructure and morphology features, which are usually overlooked in the literature, this contribution re-examines the M/F Interface damage initiation mechanism. A systematic study is performed, which accounts for different loading conditions, phase contrasts, residual stresses/strains resulting from the preceding martensitic phase transformation, as well as the possible M/F interfacial morphologies. Crystal plasticity simulations are conducted to include inter-lath retained austenite (RA) films enabling the substructure boundary sliding. The results show that the substructure boundary sliding, which is the most favourable plastic deformation mode of lath martensite, can trigger M/F Interface damage and hence control the failure behaviour of DP steels. The present finding may change the way in which M/F Interface damage initiation is understood as a critical failure mechanism in DP steels.
-
Revisiting the martensite/Ferrite Interface damage initiation mechanism: The key role of substructure boundary sliding
Acta Materialia, 2021Co-Authors: Lei Liu, Francesco Maresca, Johan P.m. Hoefnagels, Tijmen Vermeij, Marc G. D. Geers, Varvara G. KouznetsovaAbstract:Abstract Martensite/Ferrite (M/F) Interface damage plays a critical role in controlling failure of dual-phase (DP) steels and is commonly understood to originate from the large phase contrast between martensite and Ferrite. This however conflicts with a few, recent observations, showing that considerable M/F Interface damage initiation is often accompanied by apparent martensite island plasticity and weak M/F strain partitioning. In fact, martensite has a complex hierarchical structure which induces a strongly heterogeneous and orientation-dependent plastic response. Depending on the local stress state, (lath) martensite is presumed to be hard to deform based on common understanding. However, when favourably oriented, substructure boundary sliding can be triggered at a resolved shear stress which is comparable to that of Ferrite. Moreover, careful measurements of the M/F Interface structure indicate the occurrence of sharp martensite wedges protruding into the Ferrite and clear steps in correspondence with lath boundaries, constituting a jagged M/F interfacial morphology that may have a large effect on the M/F Interface behaviour. By taking into account the substructure and morphology features, which are usually overlooked in the literature, this contribution re-examines the M/F Interface damage initiation mechanism. A systematic study is performed, which accounts for different loading conditions, phase contrasts, residual stresses/strains resulting from the preceding martensitic phase transformation, as well as the possible M/F interfacial morphologies. Crystal plasticity simulations are conducted to include inter-lath retained austenite (RA) films enabling the substructure boundary sliding. The results show that the substructure boundary sliding, which is the most favourable plastic deformation mode of lath martensite, can trigger M/F Interface damage and hence control the failure behaviour of DP steels. The present finding may change the way in which M/F Interface damage initiation is understood as a critical failure mechanism in DP steels.
Sybrand Van Der Zwaag - One of the best experts on this subject based on the ideXlab platform.
-
application of the cyclic phase transformation concept for determining the effective austenite Ferrite Interface mobility
Computational Materials Science, 2014Co-Authors: Ernst Gamsjager, Hao Chen, Sybrand Van Der ZwaagAbstract:Abstract A series of cyclic partial austenite–Ferrite phase transformation computer simulation experiments have been performed to elucidate the rate controlling dissipative processes during austenite-to-Ferrite and the Ferrite-to-austenite transformation in lean C–Mn steels. The transformation kinetics is analyzed by comparing the results of two complementary sharp Interface models – one is based on the assumption of local equilibrium at the migrating Interface − in the other model diffusion in the Interface and the interfacial reaction is implemented by an effective Interface mobility but substitutional diffusion in the bulk phases is neglected. Values for effective Interface mobilities have been obtained for both the austenite-to-Ferrite transformation and vice versa. By means of effective mobilities which depend only on initial composition and temperature, the transformation kinetics has been studied for other heat treatments than used to determine the effective interfacial mobility values. Although substitutional diffusion in the bulk is not taken into account, for the low Mn alloys it is possible to obtain similar trends by the effective mobility model as provided by the local equilibrium model. At modest to high Interface velocities long range diffusion of the substitutional alloying elements can be ignored but then the effects of local diffusion processes near the Interface need to be taken into account via an effective Interface mobility. The effective mobility for the austenite-to-Ferrite transformation differs from the effective mobility during the Ferrite-to-austenite transformation in a rather essential manner.
-
Application of the cyclic phase transformation concept for determining the effective austenite/Ferrite Interface mobility
Computational Materials Science, 2014Co-Authors: Ernst Gamsjager, Hao Chen, Sybrand Van Der ZwaagAbstract:Abstract A series of cyclic partial austenite–Ferrite phase transformation computer simulation experiments have been performed to elucidate the rate controlling dissipative processes during austenite-to-Ferrite and the Ferrite-to-austenite transformation in lean C–Mn steels. The transformation kinetics is analyzed by comparing the results of two complementary sharp Interface models – one is based on the assumption of local equilibrium at the migrating Interface − in the other model diffusion in the Interface and the interfacial reaction is implemented by an effective Interface mobility but substitutional diffusion in the bulk phases is neglected. Values for effective Interface mobilities have been obtained for both the austenite-to-Ferrite transformation and vice versa. By means of effective mobilities which depend only on initial composition and temperature, the transformation kinetics has been studied for other heat treatments than used to determine the effective interfacial mobility values. Although substitutional diffusion in the bulk is not taken into account, for the low Mn alloys it is possible to obtain similar trends by the effective mobility model as provided by the local equilibrium model. At modest to high Interface velocities long range diffusion of the substitutional alloying elements can be ignored but then the effects of local diffusion processes near the Interface need to be taken into account via an effective Interface mobility. The effective mobility for the austenite-to-Ferrite transformation differs from the effective mobility during the Ferrite-to-austenite transformation in a rather essential manner.
-
in situ observation of austenite Ferrite Interface migration in a lean mn steel during cyclic partial phase transformations
Acta Materialia, 2013Co-Authors: Hao Chen, Ernst Gamsjager, Siegfried Schider, Hamideh Khanbareh, Sybrand Van Der ZwaagAbstract:Abstract High-temperature laser scanning confocal microscopy (HT LSCM) has been applied to investigate the austenite–Ferrite Interface migration during cyclic phase transformations in situ in a Fe–Mn–C alloy. It has been found that during the cyclic phase transformations the transformation proceeds via the migration of existing austenite–Ferrite Interfaces. The Interfaces migrate in a retraceable way. For the first time, the so–Called stagnant stage has been observed directly. The new in situ observations show that the Interface migration rates for Interfaces in different grains are comparable with each other prior to soft impingement, while the equilibrium migration distances for different Interfaces can be quite different, depending on the local grain size. The average Interface velocities as measured by HT LSCM are in very good agreement with the velocities derived from dilatometric data, and those are predicted by a local equilibrium transformation model.
-
In situ observation of austenite–Ferrite Interface migration in a lean Mn steel during cyclic partial phase transformations
Acta Materialia, 2013Co-Authors: Hao Chen, Ernst Gamsjager, Siegfried Schider, Hamideh Khanbareh, Sybrand Van Der ZwaagAbstract:Abstract High-temperature laser scanning confocal microscopy (HT LSCM) has been applied to investigate the austenite–Ferrite Interface migration during cyclic phase transformations in situ in a Fe–Mn–C alloy. It has been found that during the cyclic phase transformations the transformation proceeds via the migration of existing austenite–Ferrite Interfaces. The Interfaces migrate in a retraceable way. For the first time, the so–Called stagnant stage has been observed directly. The new in situ observations show that the Interface migration rates for Interfaces in different grains are comparable with each other prior to soft impingement, while the equilibrium migration distances for different Interfaces can be quite different, depending on the local grain size. The average Interface velocities as measured by HT LSCM are in very good agreement with the velocities derived from dilatometric data, and those are predicted by a local equilibrium transformation model.
-
A metallurgical interpretation of the static recrystallization kinetics of an intercritically deformed C-Mn steel
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 2004Co-Authors: Haiwen Luo, Jilt Sietsma, Sybrand Van Der ZwaagAbstract:The austenite recrystallization kinetics in the intercritical region of a C-Mn steel is investigated by means of stress relaxation tests. It is found that the Avrami exponent, n, decreases significantly with decreasing temperature, i.e., with increasing Ferrite fraction. This behavior deviates from that of austenite recrystallization in the purely austenitic state, in which case the Avrami exponent is constant and independent of temperature. To resolve the origin of the changing Avrami exponent, the influence of the austenite/Ferrite Interface boundary area and that of the spatial variation of the plastic strain in the austenite grains is modeled quantitatively. The modeling results seem to indicate that the strain heterogeneity rather than the reduced Interface boundary length is responsible for the decreasing Avrami exponent with decreasing temperature.
Chenghorng Lee - One of the best experts on this subject based on the ideXlab platform.
-
effects of lead ii oxide on processing and properties of low temperature cofirable ni cu zn Ferrite
Journal of the American Ceramic Society, 2004Co-Authors: Jauho Jean, Chenghorng Lee, Wensong KouAbstract:The effects of PbO addition on the densification, microstructure, and properties of low-temperature cofirable Ni-Cu-Zn Ferrite have been investigated. With a small amount of PbO (0.5–2 wt%) present as a dopant in the Ni-Cu-Zn Ferrite, the densification rate and final sintered density are greatly increased, but the activation energy of densification is significantly reduced. These results are attributed to a chemical reaction that occurs at the PbO/Ni-Cu-Zn Ferrite Interface, resulting in a greater amount of liquid phase and good wetting during sintering. However, the above-mentioned interfacial reaction causes segregation of CuO onto the grain boundary and dissolution of PbO into the Ferrite grains, yielding a reduction in initial permeability.
-
Effects of Lead(II) Oxide on Processing and Properties of Low‐Temperature‐Cofirable Ni‐Cu‐Zn Ferrite
Journal of the American Ceramic Society, 2004Co-Authors: Jauho Jean, Chenghorng Lee, Wensong KouAbstract:The effects of PbO addition on the densification, microstructure, and properties of low-temperature cofirable Ni-Cu-Zn Ferrite have been investigated. With a small amount of PbO (0.5–2 wt%) present as a dopant in the Ni-Cu-Zn Ferrite, the densification rate and final sintered density are greatly increased, but the activation energy of densification is significantly reduced. These results are attributed to a chemical reaction that occurs at the PbO/Ni-Cu-Zn Ferrite Interface, resulting in a greater amount of liquid phase and good wetting during sintering. However, the above-mentioned interfacial reaction causes segregation of CuO onto the grain boundary and dissolution of PbO into the Ferrite grains, yielding a reduction in initial permeability.