Influence of austenitising temperature on kinetics of phase transformations in medium carbon TRIP steel

Kokosza, A.; Pacyna, J.

doi:10.1179/1743284714y.0000000705

Cited by 19 publications

(13 citation statements)

References 26 publications

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“…Based on this and due to the fact that heat-treatment procedures mainly influence matrix properties, many authors suggest that fracture toughness of tool steel is controlled by the matrix ductility [17,[21][22][23]. Higher K Ic values as a result of higher contents of retained austenite were detected by [18,22,[24][25][26]. Further possible influencing factors of tool steel fracture toughness which were mentioned in the literature are the effects of carbides (distribution, size, interparticle spacing) [18,23,27,28] and grain size [22,29,30].…”

Section: Introductionmentioning

confidence: 94%

High strain rate behavior, transformation-induced plasticity and fracture toughness characterization of cast and additionally tempered Fe85Cr4Mo8V2C1 alloy manufactured using a rapid solidification technique

et al. 2012

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This study focuses on the characterization of the microstructures of an FeCrMoVC alloy in two states (an as-cast and a heat-treated state) as well as the compressive strain rate-dependent material and fracture toughness behavior. Both microstructures consist of martensite, retained austenite and complex carbides. Tempering results in a transformation of retained austenite into martensite, the precipitation of fine alloy carbides, and diffusion processes. High yield stresses, flow and ultimate compressive strength values at a relatively good deformability were measured. The yield and flow stresses at the onset of deformation are higher for the heat-treated state due to higher martensitic phase fractions and fine precipitations of alloy carbides respectively. Compressive deformation causes a straininduced transformation of retained austenite to a 0 -martensite. Hence, both high-strength alloys are TRIP-assisted steels (TRansformation-Induced Plasticity). However, the martensitic transformation is more pronounced in the as-cast state due to higher phase fractions of retained austenite already in the initial state. Examinations of strained microstructures showed decreased crystallite sizes with increasing deformation. It is assumed that, during plastic deformation, the amount of low angle grain boundaries increases while the incremental formation of a 0 -martensite leads to decreased crystallite size. In general, lower microstrains were determined in the heat-treated state as a consequence of stress relaxation during tempering. In comparison to commercially available tool steels, the determined fracture toughness K Ic of both variants revealed relatively high fracture toughness values. It was found that the lower shelf of K Ic is already reached at room temperature. Higher loading rates _ K resulted in lower dynamic fracture toughness K Id values. Notch fracture toughness K A measurements indicate that the critical notch tip radii of the examined materials are slightly smaller than 0.09 mm.

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Section: Introductionmentioning

confidence: 94%

High strain rate behavior, transformation-induced plasticity and fracture toughness characterization of cast and additionally tempered Fe85Cr4Mo8V2C1 alloy manufactured using a rapid solidification technique

et al. 2012

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“…[1][2][3][4][5][6] These are for example steels with carbide-free bainite [1,2,6] or steels containing martensite and retained austenite enriched with carbon [5,7]. The efficient heat treatment which allows obtaining in steel the martensitic-austenitic microstructure is called quenching & partitioning (Q&P) [8,9].…”

Section: Introductionmentioning

confidence: 99%

The Microstructure and Phase Composition of 35CrSiMN5-5-4 Steel After Quenching and Partitioning Heat Treatment

Skołek¹,

Wasiak²,

Świątnicki³

2016

Archives of Metallurgy and Materials

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The aim of the study was to characterise the microstructure of 35CrSiMn5-5-4 steel which was subjected to a new heat treatment technology of quenching and partitioning (Q&P). The parameters of the treatment were chosen on the basis of computer simulations and dilatometric studies of phase transformations occurring in steel. The transmission electron microscopy (TEM) observations of steel microstructure after the Q&P treatment revealed the presence of martensite as well as significant amount of retained austenite in form of layers between the martensite laths. The rod-like carbides in the ferritic areas were also observed, which indicates the presence of lower bainite in steel. It was found that the retained austenite content measured by means of TEM was about 28% for partitioning at 400°C and 25% for partitioning at 260°C. These results are in good agreement with the phase composition calculated theoretically as well as those determined experimentally by use of dilatometric tests.

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“…Steels with such a structure are called nanobainitic steels and they have very beneficial mechanical properties [5,6]. Residual austenite in steel provides increased plasticity and fracture toughness [8,9,10,11]. However, if the austenite content is too high, the strength value decreases.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Stepped Austempering on Phase Composition and Mechanical Properties of Nanostructured X37CrMoV5-1 Steel

Marciniak¹,

Skołek²,

Świątnicki³

2015

Archives of Metallurgy and Materials

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This paper presents the results of studies of X37CrMoV5-1 steel subjected to quenching processes with a one-step and a two-step isothermal annealing. The TEM observation revealed that steel after one-step treatment led is composed of carbide-free bainite with nanometric thickness of ferrite plates and of high volume fraction of retained austenite in form of thin layers or large blocks. In order to improve the strength parameters an attempt was made to reduce the austenite content by use of quenching with the two-step isothermal annealing. The temperature and time of each step were designed on the basis of dilatometric measurements. It was shown, that the two-step heat treatment led to increase of the bainitic ferrite content and resulted in improvement of steel's strength with no loss of steel ductility.Keywords: heat treatment, austempering, steels, nanobainite, dilatometric test W artykule przedstawiono wyniki badań stali X37CrMoV5-1 poddanej hartowaniu izotermicznemu jedno i dwu stopniowemu. Obserwacji TEM wykazały, że stal po jednostopniowym hartowaniu izotermicznym składa się z bainitu bezwęglikowego o nanometrycznej grubości płytek ferrytu poprzedzielanych cienkimi warstwami lub blokami austenitu. Wysoka plastyczność stali wynika z wysokiej zawartością fazy austenitycznej. W celu poprawy parametrów wytrzymałościowych postanowiono zmniejszyć ilość austenitu poprzez zastosowanie dwustopniowego hartowania izotermicznego. Parametry tego procesu zostały zaprojektowane na podstawie badań dylatometrycznych. Wykazano, że dwustopniowa obróbka cieplna prowadził do podwyż-szenia zawartości ferrytu bainitycznego i tym samym do poprawy wytrzymałości stali bez utraty plastyczności.

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Influence of austenitising temperature on kinetics of phase transformations in medium carbon TRIP steel

Cited by 19 publications

References 26 publications

High strain rate behavior, transformation-induced plasticity and fracture toughness characterization of cast and additionally tempered Fe85Cr4Mo8V2C1 alloy manufactured using a rapid solidification technique

High strain rate behavior, transformation-induced plasticity and fracture toughness characterization of cast and additionally tempered Fe85Cr4Mo8V2C1 alloy manufactured using a rapid solidification technique

The Microstructure and Phase Composition of 35CrSiMN5-5-4 Steel After Quenching and Partitioning Heat Treatment

The Effect of Stepped Austempering on Phase Composition and Mechanical Properties of Nanostructured X37CrMoV5-1 Steel

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