Phase Transformation from Fine-grained Austenite

Furuhara, Tadashi; Kikumoto, Kazuno; Saito, Hiroki; Sekine, Takashi; Ogawa, Tetsuya; Morito, Shigekazu; Maki, Tadashi

doi:10.2355/isijinternational.48.1038

Cited by 141 publications

(87 citation statements)

References 37 publications

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“…The number of packets per parent austenite grain is reduced with decreasing PAGS as well as the ratio d PAGS /d PS , which approaches unity. Furuhara et al [3] observed a similar behavior in an Fe-0.2C-2Mn steel for a PAGS smaller than 50 lm. In Cycle III and Cycle IV, some PAGSs are still sub-divided into a few packets, even in austenite grains of few micrometer, but it was common to observe a single packet being formed in an austenite grain for PAGS around one micrometer.…”

Section: A Effect Of Thermal Cycling On Grain Substructuresmentioning

confidence: 48%

“…Since then, thermal cycling processes have been investigated in a number of studies. [3,5,14,16] These studies highlight that microstructure refinement can be achieved effectively by successive a¢ fi c reversion processes involving rapid heating. This is also the conclusion of the present study.…”

Section: A Effect Of Thermal Cycling On Grain Substructuresmentioning

confidence: 99%

“…[3] This implies an increase of high-angle boundaries in as-quenched martensite microstructure, which are effective barriers to dislocation movement during deformation of lath martensite and strongly affect the strengthening of the material. [3,[7][8][9] PAGS reduction has other consequences for the martensitic microstructure. It leads to a reduction of the Ms temperature [10,11] and may also cause an increase of the retained austenite (RA) fraction.…”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5][6][7] Packet and block sizes are commonly observed to be reduced with a reduction of PAGS. [3] This implies an increase of high-angle boundaries in as-quenched martensite microstructure, which are effective barriers to dislocation movement during deformation of lath martensite and strongly affect the strengthening of the material. [3,[7][8][9] PAGS reduction has other consequences for the martensitic microstructure.…”

Section: Introductionmentioning

confidence: 99%

“…An interesting method for PAGS reduction and thus microstructure reduction even to submicron scale [3,4,6,[14][15][16] is the employment of a successive martensite-austenite reversion processes through rapid heating and quenching . However, there is a lack of investigations that methodically study the effect of PAGS reduction by thermal cycling on the microstructure of lath martensite.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

Hidalgo

Santofimia

2016

Metall Mater Trans A

187

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Current trends in steels are focusing on refined martensitic microstructures to obtain high strength and toughness. An interesting manner to reduce the size of martensitic substructure is by reducing the size of the prior austenite grain (PAG). This work analyzes the effect of PAGS refinement by thermal cycling on different microstructural features of as-quenched lath martensite in a 0.3C-1.6Si-3.5Mn (wt pct) steel. The application of thermal cycling is found to lead to a refinement of the martensitic microstructures and to an increase of the density of high misorientation angle boundaries after quenching; these are commonly discussed to be key structural parameters affecting strength. Moreover, results show that as the PAGS is reduced, the volume fraction of retained austenite increases, carbides are refined and the concentration of carbon in solid solution as well as the dislocation density in martensite increase. All these microstructural modifications are related with the manner in which martensite forms from different prior austenite conditions, influenced by the PAGS.

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Section: A Effect Of Thermal Cycling On Grain Substructuresmentioning

confidence: 48%

Section: A Effect Of Thermal Cycling On Grain Substructuresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

Hidalgo

Santofimia

2016

Metall Mater Trans A

187

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Strain‐Induced Development of Very Fine Ferrite‐Cementite Structures in Eutectoid Steels

Caruso

Godet

2012

Adv Eng Mater

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The development of duplex microstructures consisting of very fine ferrite grains and spheroidized cementite particles during concurrent hot deformation has been investigated by hot torsion in a eutectoid steel. It is shown that the hot deformation of the undercooled austenite at temperatures close to Ar1 induces and accelerates significantly the γ‐to‐pearlite transformation. Further deformation of the transforming pearlite does not lead only to the instantaneous spheroidization of the cementite lamellae but also refines the ferrite orientations units from 15 to 3 µm. Microstructures consisting of very fine ferrite grains (3 µm) and submicron cementite particles are produced at strain levels larger than ε = 1.5. The initial grains undergo progressive fragmentation by the generation of low angle boundaries (LABs) by dynamic recovery that progressively transform into high angle boundaries (HABs). The progressive increase of LABs misorientation is attributed to the presence of cementite particles and is referred to as continuous dynamic recrystallization (cDRX). Fine prior austenite grain size and moderate strain rates are found to promote the occurrence of cDRX. The resulting torsion textures consist of a strong 〈111〉 fiber dominated by the D {112} 〈111〉 component. During the subsequent annealing step, cementite particles coarsen preferentially at the triple junctions whereas the very fine ferrite grain are stable due to the strong pinning effect exerted by the cementite particles.

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Scale‐dependent hierarchy of structural elements in the microstructure of thermomechanical treated ferritic steels with residual austenite

Teplyakova

Gershteyn²,

Попова

et al. 2009

Materialwissenschaft Werkst

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Experimental results of the structural investigations of dislocations and carbides are presented here for four steels with ferriticcarbide structures which were subjected to different final thermal processing. The investigation was carried out using different methods which involved optical microscopy, REM, TEM and x-ray structural analysis. The complex procedures implemented permitted both investigations at intervals from the macro to the micro scale as well as detection of the total spectrum of the scale and structure levels which form during the steel's thermal treatment. As a consequence of these analyses, representative structural volume elements (RSVE) were detected which includes all relevant structural parameters, i.e. dislocation structures, precipitates and phases.Key words: ferritic steel, residual austenite; substructure; dislocation structure; scale level In der vorliegenden Arbeit werden die experimentellen Ergebnisse der Strukturuntersuchung von Versetzungen und Karbiden in vier Stählen mit ferritischer Struktur vorgestellt, wobei die Stähle unterschiedlichen abschließenden thermischen Behandlungen ausgesetzt waren. Für die Untersuchung wurden verschiedene analytische Methoden (u. a. Lichtmikroskopie, Raster-und Transmissionselektronenmikroskopie, Röntgenstrukturanalyse) eingesetzt, deren Kombination eine skalenübergreifende strukturelle Betrachtung sowohl im makroskopischen als auch im mikroskopischen Größenbereich ermöglichte. Auf diese Weise konnte ein repräsen-tatives strukturelles Volumenelement (RSVE) identifiziert werden, welches alle relevanten mikrostrukturellen Größen, wie Versetzungsstrukturen, Ausscheidungen und Phasen, beinhaltet.

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Phase Transformation from Fine-grained Austenite

Cited by 141 publications

References 37 publications

Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

Strain‐Induced Development of Very Fine Ferrite‐Cementite Structures in Eutectoid Steels

Scale‐dependent hierarchy of structural elements in the microstructure of thermomechanical treated ferritic steels with residual austenite

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