The Experts below are selected from a list of 705 Experts worldwide ranked by ideXlab platform
R Cochrane, Department Of Materials, University Of F Leeds - One of the best experts on this subject based on the ideXlab platform.
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Hypoeutectoid steel, normalised at 950°C
University of Leeds, 2010Co-Authors: Doitpoms, University Of Cambridge, R Cochrane, Department Of Materials, University Of F LeedsAbstract:A hypoeutectoid alloy (carbon composition less than eutectoid). The first phase formed upon cooling from the Austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the Remaining Austenite. At the eutectoid point the Remaining carbon enriched Austenite transforms to pearlite (a mixture of ferrite and cementite) which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition. The ferrite (light areas) is a good example of an allotriomorphic ferrite. This means that its shape does not reflect its internal crystalline symmetry as it nucleates on the Austenite grain boundaries and hence follows the shape of the boundaries, the Remaining Austenite within the ferrite then transforms to pearlite, and is surrounded by the ferrite.
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Fe, C 0.4, Mn 0.8 (wt%) steel, normalised
University of Leeds, 2010Co-Authors: Doitpoms, University Of Cambridge, R Cochrane, Department Of Materials, University Of F LeedsAbstract:A hypoeutectoid alloy (carbon composition less than eutectoid). The first phase formed upon cooling from the Austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the Remaining Austenite. At the eutectoid point the Remaining carbon enriched Austenite transforms to pearlite (a mixture of ferrite and cementite) which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition. The ferrite (light areas) is a good example of an allotriomorphic ferrite. This means that its shape does not reflect its internal crystalline symmetry as it nucleates on the Austenite grain boundaries and hence follows the shape of the boundaries, the Remaining Austenite within the ferrite then transforms to pearlite, and is surrounded by the ferrite.
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Fe, C 0.3 (wt%) steel, spheroidised carbide
University of Leeds, 2010Co-Authors: Doitpoms, University Of Cambridge, R Cochrane, Department Of Materials, University Of F LeedsAbstract:A hypoeutectoid alloy (composition less than eutectoid). The first phase formed upon cooling from the Austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the Remaining Austenite. At the eutectic point the Remaining carbon-enriched Austenite transforms to pearlite (a mixture of ferrite and cementite), which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition.Subsequent to casting the sample was annealed for a long period just below the transformation range. This induces the cementite to take on a spherical appearance. This results in a softer and more ductile alloy. This process is known as spheroidisation. The changes to the morphology of the cementite, compared with the normal plate-like appearance in freshly-formed pearlite, are clearly visible in this micrograph.
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Fe, C 0.3 (wt%) steel, spheroidised carbide
University of Leeds, 2010Co-Authors: Doitpoms, University Of Cambridge, R Cochrane, Department Of Materials, University Of F LeedsAbstract:A hypoeutectoid alloy (composition less than eutectoid). The first phase formed upon cooling from the Austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the Remaining Austenite. At the eutectic point the Remaining carbon-enriched Austenite transforms to pearlite (a mixture of ferrite and cementite), which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition.Subsequent to casting the sample was annealed for a long period just below the transformation range. This induces the cementite to take on a spherical appearance. This results in a softer and more ductile alloy. This process is known as spheroidisation. The changes to the morphology of the cementite cannot be seen clearly in this micrograph, but they are more apparent at higher magnification (see micrograph 242)
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Hypoeutectoid steel, normalised at 1100°C
University of Leeds, 2010Co-Authors: Doitpoms, University Of Cambridge, R Cochrane, Department Of Materials, University Of F LeedsAbstract:A hypoeutectoid alloy (carbon composition less than eutectoid). The first phase formed upon cooling from the Austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the Remaining Austenite. At the eutectoid point the Remaining carbon enriched Austenite transforms to pearlite (a mixture of ferrite and cementite) which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition. The ferrite (light areas) is a good example of an allotriomorphic ferrite. This means that its shape does not reflect its internal crystalline symmetry as it nucleates on the Austenite grain boundaries and hence follows the shape of the boundaries, the Remaining Austenite within the ferrite then transforms to pearlite, and is surrounded by the ferrite. The large size of the areas of pearlite arises due to the high normalisation temperature which causes the Austenite grains to grow large.
Doitpoms, University Of Cambridge - One of the best experts on this subject based on the ideXlab platform.
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Hypoeutectoid steel, normalised at 950°C
University of Leeds, 2010Co-Authors: Doitpoms, University Of Cambridge, R Cochrane, Department Of Materials, University Of F LeedsAbstract:A hypoeutectoid alloy (carbon composition less than eutectoid). The first phase formed upon cooling from the Austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the Remaining Austenite. At the eutectoid point the Remaining carbon enriched Austenite transforms to pearlite (a mixture of ferrite and cementite) which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition. The ferrite (light areas) is a good example of an allotriomorphic ferrite. This means that its shape does not reflect its internal crystalline symmetry as it nucleates on the Austenite grain boundaries and hence follows the shape of the boundaries, the Remaining Austenite within the ferrite then transforms to pearlite, and is surrounded by the ferrite.
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Fe, C 0.4, Mn 0.8 (wt%) steel, normalised
University of Leeds, 2010Co-Authors: Doitpoms, University Of Cambridge, R Cochrane, Department Of Materials, University Of F LeedsAbstract:A hypoeutectoid alloy (carbon composition less than eutectoid). The first phase formed upon cooling from the Austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the Remaining Austenite. At the eutectoid point the Remaining carbon enriched Austenite transforms to pearlite (a mixture of ferrite and cementite) which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition. The ferrite (light areas) is a good example of an allotriomorphic ferrite. This means that its shape does not reflect its internal crystalline symmetry as it nucleates on the Austenite grain boundaries and hence follows the shape of the boundaries, the Remaining Austenite within the ferrite then transforms to pearlite, and is surrounded by the ferrite.
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Fe, C 0.3 (wt%) steel, spheroidised carbide
University of Leeds, 2010Co-Authors: Doitpoms, University Of Cambridge, R Cochrane, Department Of Materials, University Of F LeedsAbstract:A hypoeutectoid alloy (composition less than eutectoid). The first phase formed upon cooling from the Austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the Remaining Austenite. At the eutectic point the Remaining carbon-enriched Austenite transforms to pearlite (a mixture of ferrite and cementite), which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition.Subsequent to casting the sample was annealed for a long period just below the transformation range. This induces the cementite to take on a spherical appearance. This results in a softer and more ductile alloy. This process is known as spheroidisation. The changes to the morphology of the cementite, compared with the normal plate-like appearance in freshly-formed pearlite, are clearly visible in this micrograph.
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Fe, C 0.3 (wt%) steel, spheroidised carbide
University of Leeds, 2010Co-Authors: Doitpoms, University Of Cambridge, R Cochrane, Department Of Materials, University Of F LeedsAbstract:A hypoeutectoid alloy (composition less than eutectoid). The first phase formed upon cooling from the Austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the Remaining Austenite. At the eutectic point the Remaining carbon-enriched Austenite transforms to pearlite (a mixture of ferrite and cementite), which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition.Subsequent to casting the sample was annealed for a long period just below the transformation range. This induces the cementite to take on a spherical appearance. This results in a softer and more ductile alloy. This process is known as spheroidisation. The changes to the morphology of the cementite cannot be seen clearly in this micrograph, but they are more apparent at higher magnification (see micrograph 242)
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Hypoeutectoid steel, normalised at 1100°C
University of Leeds, 2010Co-Authors: Doitpoms, University Of Cambridge, R Cochrane, Department Of Materials, University Of F LeedsAbstract:A hypoeutectoid alloy (carbon composition less than eutectoid). The first phase formed upon cooling from the Austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the Remaining Austenite. At the eutectoid point the Remaining carbon enriched Austenite transforms to pearlite (a mixture of ferrite and cementite) which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition. The ferrite (light areas) is a good example of an allotriomorphic ferrite. This means that its shape does not reflect its internal crystalline symmetry as it nucleates on the Austenite grain boundaries and hence follows the shape of the boundaries, the Remaining Austenite within the ferrite then transforms to pearlite, and is surrounded by the ferrite. The large size of the areas of pearlite arises due to the high normalisation temperature which causes the Austenite grains to grow large.
Lizhan Han - One of the best experts on this subject based on the ideXlab platform.
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Decomposition characteristic of Austenite retained in GCr15 bearing steel modified by addition of 1.3 wt.% silicon during tempering
Elsevier, 2019Co-Authors: Zhihui Chen, Lizhan HanAbstract:The decomposition characteristic of Austenite retained in a GCr15 bearing steel modified by the addition of 1.3 wt.% silicon during tempering was investigated by microstructural observation, X-ray determination, and dilatometric experiment. The addition of 1.3 wt.% silicon in the modified GCr15 bearing steel significantly increases the amount of Remaining Austenite. After tempering at 300 °C for 96 h, 18 vol.% of Austenite with 1.6 wt.% carbon remained. Austenite decomposition during the tempering is a bainitic transformation, and occurs via the displacive mechanism, following by carbon partitioning into the Remaining Austenite. The bainite transformation becomes slower as the carbon enrichment in Austenite improves. In contrast, carbide precipitation accelerates the bainite transformation kinetics. However, the carbon enrichment in Austenite associated with carbon partitioning and the precipitation of carbides are competitive processes, with their relative rates depending on temperature. Consequently, the improvement in the thermal stability of Austenite is ascribed to the combined effects of the partitioning of carbon into Austenite and the suppression of carbide precipitation. Keywords: Bainite, Carbon partitioning, Cementite precipitation, Retained Austenite (RA), Temperin
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decomposition characteristic of Austenite retained in gcr15 bearing steel modified by addition of 1 3 wt silicon during tempering
Journal of materials research and technology, 2017Co-Authors: Zhihui Chen, Lizhan HanAbstract:Abstract The decomposition characteristic of Austenite retained in a GCr15 bearing steel modified by the addition of 1.3 wt.% silicon during tempering was investigated by microstructural observation, X-ray determination, and dilatometric experiment. The addition of 1.3 wt.% silicon in the modified GCr15 bearing steel significantly increases the amount of Remaining Austenite. After tempering at 300 °C for 96 h, 18 vol.% of Austenite with 1.6 wt.% carbon remained. Austenite decomposition during the tempering is a bainitic transformation, and occurs via the displacive mechanism, following by carbon partitioning into the Remaining Austenite. The bainite transformation becomes slower as the carbon enrichment in Austenite improves. In contrast, carbide precipitation accelerates the bainite transformation kinetics. However, the carbon enrichment in Austenite associated with carbon partitioning and the precipitation of carbides are competitive processes, with their relative rates depending on temperature. Consequently, the improvement in the thermal stability of Austenite is ascribed to the combined effects of the partitioning of carbon into Austenite and the suppression of carbide precipitation.
Dierk Raabe - One of the best experts on this subject based on the ideXlab platform.
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the impact of grain scale strain localization on strain hardening of a high mn steel real time tracking of the transition from the γ e α transformation to twinning
Acta Materialia, 2020Co-Authors: Dirk Ponge, I Souza R Filho, Aniruddha Dutta, D R Almeida, M J R Sandim, H R Z Sandim, Dierk RaabeAbstract:Abstract Strain partitioning and localization were investigated in a high-Mn steel (17.1 wt.% Mn) during tensile testing by a correlative probing approach including in-situ synchrotron X-ray diffraction, micro- digital image correlation (μ-DIC) and electron microscopy. By combining Warren's theory with the μ-DIC analysis, we monitored the formation of planar faults (stacking faults and mechanical twins) and correlated them with the local strain partitioning behavior within the microstructure. Starting with an initial microstructure of Austenite (γ) and athermally formed e- and α’-martensite, strain accumulates preferentially near the γ/e interfaces during tensile straining. The local microscopic von Mises strain (evM) maps obtained from μ-DIC probing show that these local strain gradients produce local strain peaks approximately twice as high as the imposed macroscopic engineering strain (e), thus locally triggering formation of e-martensite already at early yielding. The interior of the Remaining Austenite, without such interfacial strain peaks, remained nearly devoid of planar faults. The local strain-driven growth of the e-domains occurs concomitantly with the α’-martensite formation. At intermediate macroscopic applied strains, Austenite grain size is considerably reduced to a few nanometers and the associated γ/e interfacial microscopic strain peaks increase in magnitude. This scenario favors twinning to emerge as a competing strain hardening mechanism at engineering strain levels from e = 0.075 onwards. At large tensile strains, the γ → e → α’ transformation rates tend to cease making both twinning and SFs formation to operate as the main strain hardening mechanisms. The findings shed light on the transformation micro-mechanisms in multiphase Mn-TRIP steels by revealing how strain localization among the constituents can directly influence the kinetics of the competing strain hardening mechanisms.
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growth of bainitic ferrite and carbon partitioning during the early stages of bainite transformation in a 2 mass silicon steel studied by in situ neutron diffraction tem and apt
Journal of Applied Crystallography, 2016Co-Authors: Iliana B Timokhina, Dierk Raabe, Hossein Beladi, Klausdieter Liss, Khushboo Rakha, Xiangyuan Xiong, Peter HodgsonAbstract:In situ neutron diffraction, transmission electron microscopy (TEM) and atom probe tomography (APT) have been used to study the early stages of bainite transformation in a 2 mass% Si nano-bainitic steel. It was observed that carbon redistribution between the bainitic ferrite and retained Austenite at the early stages of the bainite transformation at low isothermal holding occurred in the following sequence: (i) formation of bainitic ferrite nuclei within carbon-depleted regions immediately after the beginning of isothermal treatment; (ii) carbon partitioning immediately after the formation of bainitic ferrite nuclei but substantial carbon diffusion only after 33 min of bainite isothermal holding; (iii) formation of the carbon-enriched Remaining Austenite in the vicinity of bainitic laths at the beginning of the transformation; (iv) segregation of carbon to the dislocations near the Austenite/ferrite interface; and (v) homogeneous redistribution of carbon within the Remaining Austenite with the progress of the transformation and with the formation of bainitic ferrite colonies. Bainitic ferrite nucleated at internal defects or bainite/Austenite interfaces as well as at the prior Austenite grain boundary. Bainitic ferrite has been observed in the form of an individual layer, a colony of layers and a layer with sideplates at the early stages of transformation.
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atomic scale analysis of carbon partitioning between martensite and Austenite by atom probe tomography and correlative transmission electron microscopy
Acta Materialia, 2014Co-Authors: Yuki Toji, Michael Herbig, Pyuckpa Choi, Hiroshi Matsuda, Dierk RaabeAbstract:Abstract Carbon partitioning between ferritic and austenitic phases is essential for Austenite stabilization in the most advanced steels such as those produced by the quenching and partitioning (Q&P) process. The atomistic analysis of the carbon partitioning in Q&P alloys is, however, difficult owing to the simultaneous occurrence of bainite transformation, which can also contribute to carbon enrichment into Remaining Austenite and hence overlap with the carbon partitioning from martensite into Austenite. Therefore, we provide here a direct atomic-scale evidence of carbon partitioning from martensite into Austenite without the presence of bainite transformation. Carbon partitioning is investigated by means of atom probe tomography and correlative transmission electron microscopy. A model steel (Fe–0.59 wt.% C (2.7 at.% C)–2.0 wt.% Si–2.9 wt.% Mn) with martensite finish temperature below room temperature was designed and used in order to clearly separate the carbon partitioning between martensite and Austenite from the bainite transformation. The steel was austenitized at 900 °C, then water-quenched and tempered at 400 °C. Approximately 8 vol.% retained Austenite existed in the as-quenched state. We confirmed by X-ray diffraction and dilatometry that Austenite decomposition via bainite transformation did not occur during tempering. No carbon enrichment in Austenite was observed in the as-quenched specimen. On the other hand, clear carbon enrichment in Austenite was observed in the 400 °C tempered specimens with a carbon concentration inside the Austenite of 5–8 at.%. The results hence quantitatively revealed carbon partitioning from martensite to Austenite, excluding bainite transformation during the Q&P heat treatment.
Peter Hodgson - One of the best experts on this subject based on the ideXlab platform.
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growth of bainitic ferrite and carbon partitioning during the early stages of bainite transformation in a 2 mass silicon steel studied by in situ neutron diffraction tem and apt
Journal of Applied Crystallography, 2016Co-Authors: Iliana B Timokhina, Dierk Raabe, Hossein Beladi, Klausdieter Liss, Khushboo Rakha, Xiangyuan Xiong, Peter HodgsonAbstract:In situ neutron diffraction, transmission electron microscopy (TEM) and atom probe tomography (APT) have been used to study the early stages of bainite transformation in a 2 mass% Si nano-bainitic steel. It was observed that carbon redistribution between the bainitic ferrite and retained Austenite at the early stages of the bainite transformation at low isothermal holding occurred in the following sequence: (i) formation of bainitic ferrite nuclei within carbon-depleted regions immediately after the beginning of isothermal treatment; (ii) carbon partitioning immediately after the formation of bainitic ferrite nuclei but substantial carbon diffusion only after 33 min of bainite isothermal holding; (iii) formation of the carbon-enriched Remaining Austenite in the vicinity of bainitic laths at the beginning of the transformation; (iv) segregation of carbon to the dislocations near the Austenite/ferrite interface; and (v) homogeneous redistribution of carbon within the Remaining Austenite with the progress of the transformation and with the formation of bainitic ferrite colonies. Bainitic ferrite nucleated at internal defects or bainite/Austenite interfaces as well as at the prior Austenite grain boundary. Bainitic ferrite has been observed in the form of an individual layer, a colony of layers and a layer with sideplates at the early stages of transformation.