Thermal Mechanisms of Grain and Packet Refinement in a Lath Martensitic Steel.

Kim, H. J.; Kim, Y. H.; Morris, J. W.

doi:10.2355/isijinternational.38.1277

Cited by 67 publications

(39 citation statements)

References 2 publications

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“…Kim et al [6] noticed that rapid reversion treatments break-up the alignment of blocks in packets to create ultrafine-grained martensite. This fact is also observed in the present study.…”

Section: A Effect Of Thermal Cycling On Grain Substructuresmentioning

confidence: 99%

“…No preferential direction of blocks is developed from cycling, in contrast with the observations of Kim. [6] B.…”

Section: A Effect Of Thermal Cycling On Grain Substructuresmentioning

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.…”

Section: Introductionmentioning

confidence: 99%

“…Apart from the formermentioned implications of PAGS reduction, block orientations, which have an important role in mechanical response, [8] can be modified by thermal cycling and aligned in preferential directions. [6] The present work explores the process of thermal cycling as a method to reduce PAGS and analyze further formation of lath martensite upon quenching. In this research, a 0.3C-1.5Si-3.5Mn steel was subjected to different heat treatments consisting of subsequent rapid austenitizing and quenching thermal cycles in order to reduce the PAGS.…”

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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“…Kim et al [6] noticed that rapid reversion treatments break-up the alignment of blocks in packets to create ultrafine-grained martensite. This fact is also observed in the present study.…”

Section: A Effect Of Thermal Cycling On Grain Substructuresmentioning

confidence: 99%

“…No preferential direction of blocks is developed from cycling, in contrast with the observations of Kim. [6] B.…”

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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Austenite Grain Coarsening Behaviour in a Medium Carbon Si-Cr Spring Steel with and without Vanadium

Barani

Ponge

et al. 2006

steel research international

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The austenite grain coarsening behaviour in a medium carbon Si‐Cr spring steel with and without vanadium was investigated by the thermal etching method. This method is efficient when the austenitization temperature is not lower than 900 °C. The average grain sizes on the surfaces of the samples determined by thermal etching vary little from those in the bulk as revealed by chemical etching. The austenite grain coarsening behaviour of the steel with vanadium can be classified in three temperature regimes. Below a critical temperature the vanadium addition is effective to impede grain growth and fine grains are observed. The austenite grain size was significantly smaller than in the steel without vanadium. In a medium temperature regime the steel with vanadium exhibits a bimodal grain size distribution. Above the dissolution temperature of vanadium carbides normal grain growth is observed. An equation was set up to predict the grain coarsening behaviour in the steel without vanadium. The results show how the austenite grain size, which is very important for the toughness and ductility of the spring steels, can be controlled by microalloying with vanadium.

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Strong and Ductile Martensitic Steels for Automotive Applications

Barani

Ponge

Raabe

2006

steel research international

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The limits of strength and ductility of a medium-carbon silicon chromium spring steel are investigated for the case of conventional heat treatment including austenitization, quench ing and tempering. The effect of phosphorus and austenite deformation prior to quenching was studied by measuring mechanical propert ies after quenching and tempering and by microstructural investigation. Strong influence of phosphorus on the ductility is observed for the quenched and tempered martensite without prior austenite deformation. The minimum in ductility found after tempering at 350°C is explained by the formation of cementite and grain boundary segregation of phosphorus. Two thermomechanical treatments were tested involving different austenite cond itions produced by variation of the deformation temperature. The deformed cond itions, recrystallized or work-hardened, exh ibit higher ductility at all tempering temperatures tested. A comb ined thermomechanical treatment is proposed that provides the highest ductility after tempering at 30QoC independent of the phosphorus content. All thermomechanical treatments described in this study refine or eliminate carbide films at prior austenite grain boundaries. It was found possible to increase the tensile strength and the fatigue limit by deformation of austenite prior to quenching while maintaining or increasing the ductility level.

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Thermal Mechanisms of Grain and Packet Refinement in a Lath Martensitic Steel.

Cited by 67 publications

References 2 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

Austenite Grain Coarsening Behaviour in a Medium Carbon Si-Cr Spring Steel with and without Vanadium

Strong and Ductile Martensitic Steels for Automotive Applications

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