Modelling distribution of microstructure during hot rolling of stainless steel

McLaren, A. J.; Sellars, C. M.

doi:10.1179/026708392790170180

Cited by 15 publications

(11 citation statements)

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“…Strain rate exponents equal to Ϫ0.38 are commonly reported for Type 304 and Type 316 steels in the literature. [22][23][24] All these values are relatively high compared to the values obtained for C and C-Mn steels (Ϫ0.11), medium carbon steels (Ϫ0.13) and also Ti-steels (Ϫ0.12). 8,25,26) Between these two values, the strain rate exponents for Nb and Nb-Ti and Mo steels are measured to be of the order of Ϫ0.23, 8,16) which value has also been used in the development of the regression models for kinetics and activation energy of SRX.…”

Section: Powers Of Strain and Strain Ratementioning

confidence: 98%

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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Section: Powers Of Strain and Strain Ratementioning

confidence: 98%

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

2007

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“…The results (Table 2) show that activation energy depends on temperature and strain rate. Analogous dependence of deformation parameters on the value of activation energy was observed in other alloys systems and metals [19,20]. One cannot, however, generalize in respect to the strain rate and temperature, the tendency in the change of activation energy for all type of materials.…”

Section: Discussionmentioning

confidence: 64%

“…The present research work contributes some new information about the precipitation process which occurs in solution treated nickel based superalloy deformed at elevated temperatures and was inspired by the studies of previous researches performed on Cu-Ni-Si-Cr-Mg, Cu-Ti and low carbon steel [1][2][3][4][5][6]14,20]. The strain/precipitation interaction have revealed much more complex structural processes than those reported for HSLA steels [4].…”

Section: Introductionmentioning

confidence: 89%

The Influence of Hot-Deformation Parameters on the Mechanical Properties and Precipitation Process in Nickel Based Superalloy

Nowotnik¹

2008

Superalloys 2008 (Eleventh International Symposium)

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Experimental results on hot deformation and dynamic structural processes of nickel based alloy Inconel 718 are reviewed. The focus is the analysis of dynamic precipitation processes which operate during hot deformation of these materials at elevated temperatures. Hot compression tests were performed on the solution treated precipitation hardenable nickel based superalloy Inconel 718 at 720-1150°C with a constant true strain rates of 10 -4 and 4x10 -4 s -1 . True stress -true strain curves and microstructure analysis of the deformed nickel based superalloy is presented. The properties and dynamic behaviour are explained through observation of the microstructure using standard optical, scanning and transmission electron microscopy. Structural observations of solution treated Inconel 718 deformed at high temperatures, reveal non uniform deformation effects. The distribution of molybdenum-rich and niobium-rich carbides were affected by localized flow within the strain range investigated at relatively low deformation temperatures 720 -850°C. Microstructural examination of the alloy also shows that shear banding, cavity growth and intergranular cracks penetrating through the whole grains were responsible for decreased flow stresses at temperature of 720, 800 and 850°C and might result in sample fracture at larger strains. On the basis of the measured flow stress activation energies of high-temperature deformation processes were estimated. The mathematical dependence of the effect of flow stress on temperature and strain rate (σ pl -T and σ pl -• ε ) as well as compression data were used to determine material's constants. These constants allowed the derivation of a formula that describes the relationship between strain rate ( • ε ), deformation temperature (T) and flow stress σ pl . Interaction of precipitates developed during deformation below the solvus temperature and heterogeneous deformation (flow localization) can become a significant aspect of high temperature performance of precipitation hardenable alloys. This interaction could also potentially allow production of specific microstructures in deformed materials. The contribution of flow localization to the strain hardening or flow softening and the flow stress-strain behavior during hot deformation of precipitation hardenable alloys is still a subject of extensive research.

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“…Additionally the microstructure was examined using standard optical and electron microscopy techniques, SEM (Hitachi S-3400) and TEM (STEM) -(Jeol 2100). The present research work contributes some new information about the precipitation process which occurs in solution treated nickel based superalloy deformed at elevated temperatures and was inspired by the studies of previous researches performed on Cu-Ni-Si-Cr-Mg, Cu-Ti and low carbon steel [1][2][3][4][5][6]14,20]. The strain/precipitation interaction have revealed much more complex structural processes than those reported for HSLA steels [4].…”

Section: Methodsmentioning

confidence: 89%

Effect of Thermomechanical Working on the Microstructure and Mechanical Properties of Hot Pressed Superalloy Inconel 718

Nowotnik¹,

Sieniawski²

2010

7th International Symposium on Superalloy 718 and Derivatives (2010)

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Modelling distribution of microstructure during hot rolling of stainless steel

Cited by 15 publications

References 1 publication

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

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

The Influence of Hot-Deformation Parameters on the Mechanical Properties and Precipitation Process in Nickel Based Superalloy

Effect of Thermomechanical Working on the Microstructure and Mechanical Properties of Hot Pressed Superalloy Inconel 718

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