Recrystallisation rates in austenite measured by double compression and stress relaxation methods

Perttula, Juha; Karjalainen, L.P.

doi:10.1179/026708398790290578

Cited by 23 publications

(25 citation statements)

References 6 publications

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“…Stress relaxation has been shown to be an effective method to determine the recrystallization kinetics in hot-deformed austenite and utilized extensively. 18,19) Advantages of the method compared to conventional double-hit techniques are that a single test provides a complete recrystallized fraction vs time curve and that the static recovery can de distinguished from the static recrystallization. Also, very fast metadynamic recrystallization kinetics can be recorded.…”

Section: Methodsmentioning

confidence: 99%

Effect of Silicon and Aluminium on Austenite Static Recrystallization Kinetics in High-strength TRIP-aided Steels

et al. 2012

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Section: Methodsmentioning

confidence: 99%

Effect of Silicon and Aluminium on Austenite Static Recrystallization Kinetics in High-strength TRIP-aided Steels

et al. 2012

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“…The flow stress at 5 % total reloading strain was adopted in computing the recrystallized fraction to exclude the effect of recovery from the softening data, as described elsewhere. 9) Microstructures were examined in an optical microscope (OM) as well as in a scanning electron microscope equipped with an electron back-scattered diffraction device (SEM-EBSD).…”

mentioning

confidence: 99%

High Temperature Flow Stress and Recrystallization Behavior of High-Mn TWIP Steels

2007

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The flow stress behavior and recrystallization kinetics in the hot rolling temperature range have been investigated in five Fe-Mn-Al (Mn: 25 wt%, Al: 0-8 wt%) TWIP steels by compression testing on a Gleeble simulator. Results were compared with corresponding properties of carbon and austenitic stainless steels. Microstructures were examined by electron microscopy. The results show that the flow stress level of the TWIP steels is considerably higher than that of low-carbon steels and depended on the Al concentration close to 6 wt%, while the structure is austenitic at hot rolling temperatures. At higher Al contents, the flow stress level becomes significantly lowered due to the presence of ferrite. The static recrystallization kinetics is slower compared to that of carbon steels, but it is faster than typical of Nb-microalloyed or austenitic stainless steels. High Mn content is a reason for the high flow stress as well as for slow softening. Al has a minor role only, but in the case of austenitic-ferritic structure, softening of the ferrite phase occurs very rapidly that also contributes to overall faster softening. The grain size is effectively refined by the dynamic and static recrystallization processes.KEY WORDS: high-Mn steels; Al alloying; austenite; flow stress; recrystallization.ISIJ International, Vol. 47 (2007), No. 6, specimens were compressed in a single hit to the true strain of 0.8 at a constant true strain rate that was varied between 0.005 and 5 s Ϫ1. The SRX kinetics of the steels was studied by the double-hit compression technique using different temperatures (900-1 100°C), strains (0.11-0.4) and strain rates (0.01-5 s Ϫ1). The initial grain size of the steels was about 140 mm, as excluding the annealing twin boundaries. The flow stress at 5 % total reloading strain was adopted in computing the recrystallized fraction to exclude the effect of recovery from the softening data, as described elsewhere.9) Microstructures were examined in an optical microscope (OM) as well as in a scanning electron microscope equipped with an electron back-scattered diffraction device (SEM-EBSD). Results and Discussion Flow Stress and Dynamic RecrystallizationAs examples of the constitutive behavior of the steels, typical true stress-true strain curves for the high-Mn and reference steels are displayed in Fig. 1, as compressed at the strain rates of 0.1 s Ϫ1 and 5 s Ϫ1. In Fig. 1(a), it is seen that at 0.1 s Ϫ1, the 25Mn1Al steel exhibits peak stress behavior, even though the peaks are very broad, particularly at 950°C. The peak strain is rather small, about 0.25, 0.4 and 0.5 at 1 100, 1 000 and 950°C, respectively. 25Mn1Al steel possesses much higher deformation resistance than the low-C steel. Figures 1(b) and 1(c) clearly demonstrate that the flow resistance of high-Mn steels is increased by Mn and Al alloying. The flow stress of 25Mn steel is much higher than those of low-C and Nb-bearing steels, and among the Albearing steels, flow stress increases with Al content up to 3% ( Fig. 1(b)) or up to 6 % ( Fig. 1(c))....

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“…To investigate SRx of austenite, the stress relaxation method (Zisman et al 2012;Perttula & Karjalainen 1998) was implemented on a Gleeble 3800 simulator. The selected degrees of 0.25 and 0.10 of single strains correspond, respectively, to the maximum thickness reduction during rough rolling and the average reduction in finish rolling of the investigated steels.…”

Section: Static Recrystallization Experimentsmentioning

confidence: 99%

“…The selected degrees of 0.25 and 0.10 of single strains correspond, respectively, to the maximum thickness reduction during rough rolling and the average reduction in finish rolling of the investigated steels. Distinct changes in the softening rate dσ/dt allow determination of the incubation period of SRx and the time span of its primary stage (Zisman et al 2012;Perttula & Karjalainen 1998). Stress relaxation curves for austenite of F620 alloyed with V and Nb, correspondingly, are indicated in Figs.…”

Section: Static Recrystallization Experimentsmentioning

confidence: 99%

Recrystallization-based formation of uniform fine-grained austenite structure before polymorphic transition in high-strength steels for Arctic applications

Layus

Kah

Zisman

et al. 2016

Int J Mech Mater Eng

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Background: Growing demand for materials suitable for Arctic marine constructions necessitates the development of lowcost steels with excellent low-temperature properties. One way of addressing this issue is to obtain a finegrained structure by careful control of the recrystallization process. Methods: The research methods used in this paper includes conducting experiments and making observations. The study investigates mechanisms of grain structure formation in low-carbon cold-resistant F620 steels additionally alloyed with Nb or V during hot plastic deformation. Results: The obtained results evidence that static recrystallization is the most effective means to refine the austenite structure under conditions of industrial rolling. On this basis, a temperature-strain scheme of fractional hot rolling is proposed that provides the most refined uniform structures of bainite and/or martensite after quenching. Additionally, the results show that substitution of the alloying element V by Nb makes the structure of the hot-rolled austenite more finely dispersed. Conclusions: New cold-resistant F620 steels for Arctic applications alloyed with Nb of 50-mm thickness were produced utilizing the research results. These grades of steels have reduced alloying content and exhibit improved properties, in particular, cold resistance down to −60°С and high fracture toughness at −50°С.

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Recrystallisation rates in austenite measured by double compression and stress relaxation methods

Cited by 23 publications

References 6 publications

Effect of Silicon and Aluminium on Austenite Static Recrystallization Kinetics in High-strength TRIP-aided Steels

Effect of Silicon and Aluminium on Austenite Static Recrystallization Kinetics in High-strength TRIP-aided Steels

High Temperature Flow Stress and Recrystallization Behavior of High-Mn TWIP Steels

Recrystallization-based formation of uniform fine-grained austenite structure before polymorphic transition in high-strength steels for Arctic applications

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