scholarly journals Effect of Hot Deformation on Phase Transformation Kinetics in Isothermally Annealed 3Mn-1.6Al Steel

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5817
Author(s):  
Adam Skowronek ◽  
Mateusz Morawiec ◽  
Aleksandra Kozłowska ◽  
Wojciech Pakieła
Keyword(s):  
Hot Deformation ◽  
Isothermal Holding ◽  
Temperature Deformation ◽  
Slowing Down ◽  
Ferrite Transformation ◽  
Hardness Tests ◽  
Medium Mn Steel ◽  
Dilatometric Studies ◽  
Coiling Process ◽  
Kinetics Of

The kinetics of ferritic transformation and the corresponding microstructural evolution in 0.17C-3.1Mn-1.6Al-0.04Nb-0.22Mo-0.22Si medium-Mn steel during isothermal annealing was investigated in dilatometric studies. The material was subjected to thermal and thermo-mechanical treatments aimed at obtaining, by the austenite → ferrite transformation, a sufficient fraction of ferrite to stabilize the retained austenite by C and eventual Mn partitioning. The samples were isothermally held for 5 h in a temperature range from 600 to 750 °C to simulate simplified temperature conditions of an industrial coiling process following hot rolling. Some of the samples were plastically deformed at a temperature of 900 °C before isothermal holding in order to study the effect of hot deformation on the kinetics of phase transformations. After the dilatometric investigations the material was subjected to light and scanning electron microscopy to reveal relationships between the holding temperature, deformation and microstructure evolution. Hardness tests were performed to assess the mechanical behavior. A significant effect of manganese in slowing down diffusional transformations during the cooling of steel was found. The influence of austenite deformation on the kinetics of austenite to ferrite transformation was noted. The plastically deformed samples showed an accelerated start of ferritic transformation and the extension of its range. During dilatometric tests, low-range dynamic ferritic transformation was recorded, which was also confirmed by the microscopic tests.

scholarly journals DEVELOPMENT OF THE METAL RHEOLOGY MODEL OF HIGH-TEMPERATURE DEFORMATION FOR MODELING BY FINITE ELEMENT METHOD

2019 ◽  
Vol 2 ◽  
pp. 52-60 ◽  
Author(s):  
Oleg Markov ◽  
Oleksiy Gerasimenko ◽  
Leila Aliieva ◽  
Alexander Shapoval
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Relaxation ◽  
Hot Deformation ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Software Systems ◽  
Elastic Model ◽  
Communication Model ◽  
Element Method

It is shown that when modeling the processes of forging and stamping, it is necessary to take into account not only the hardening of the material, but also softening, which occurs during hot processing. Otherwise, the power parameters of the deformation processes are precisely determined, which leads to the choice of more powerful equipment. Softening accounting (processes of stress relaxation) will allow to accurately determine the stress and strain state (SSS) of the workpiece, as well as the power parameters of the processes of deformation. This will expand the technological capabilities of these processes. Existing commercial software systems for modeling hot plastic deformations based on the finite element method (FEM) do not allow this. This is due to the absence in these software products of the communication model of the component deformation rates and stresses, which would take into account stress relaxation. As a result, on the basis of the Maxwell visco-elastic model, a relationship is established between deformation rates and stresses. The developed model allows to take into account the metal softening during a pause after hot deformation. The resulting mathematical model is tested by experiment on different steels at different temperatures of deformation. The process of steels softening is determined using plastometers. It is established experimentally that the model developed by 89 ... 93 % describes the rheology of the metal during hot deformation. The relationship between the components of the deformation rates and stresses is established, which allows to obtain a direct numerical solution of plastic deformation problems without FED iterative procedures, taking into account the real properties of the metal during deformation. As a result, the number of iterations and calculations has significantly decreased.

Microstructure Evolution and Coarsening Mechanism of 7075 Semi-Solid Aluminum Alloy Pre-Deformed by ECAP Method

2016 ◽  
Vol 256 ◽  
pp. 294-300 ◽  
Author(s):  
Jin Long Fu ◽  
Yu Wei Wang ◽  
Kai Kun Wang ◽  
Xiao Wei Li
Keyword(s):  
Aluminum Alloy ◽  
Solid State ◽  
Ostwald Ripening ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Angular Pressing ◽  
Average Grain Size ◽  
Semi Solid ◽  
Equiaxed Grains ◽  
Kinetics Of

To investigate the influence of refined grains on the microstructure of 7075 aluminum alloy in semi-solid state, a new strain induced melting activation (SIMA) method was put forward containing two main stages: pre-deformation with equal channel angular pressing (ECAP) method and isothermally holding in the semi-solid temperature range. The breaking up and growth mechanisms of the grains and kinetics of equiaxed grains coarsening during the semi-solid holding were investigated. The results showed that the average grain size after ECAP extrusion decreased significantly, e.g., microstructure with average globular diameter less than 5μm was achieved after four-pass ECAP extrusion. Obvious grain coarsening had been found during isothermal holding in the semi-solid state and the roundness of the grains increased with the increasing holding time. The proper microstructure of 66.8μm in diameter and 1.22 in shape factor was obtained under proper soaking condition (at 590°C for 15 min). Two coarsening mechanisms, namely, coalescence in lower liquid fraction and Ostwald ripening in higher liquid fraction contributed to the grain growth process.

The increase in intracellular pH associated with Xenopus egg activation is a Ca(2+)-dependent wave

1992 ◽  
Vol 101 (1) ◽  
pp. 55-67 ◽  
Author(s):  
N. Grandin ◽  
M. Charbonneau
Keyword(s):  
Cell Cycle ◽  
Intracellular Ph ◽  
Egg Activation ◽  
Free Calcium ◽  
Slowing Down ◽  
M Phase ◽  
Xenopus Egg ◽  
General Slowing ◽  
The Impact ◽  
Kinetics Of

In Xenopus eggs, the transient increase in intracellular free calcium ([Ca2+]i), or Ca2+ transient, which occurs 1–3 min after egg activation, is likely to be partly responsible for the release of the cell cycle blockade. In the present study, we have used microinjection of BAPTA or EGTA, two potent chelators of Ca2+, to buffer [Ca2+]i at various steps during Xenopus egg activation and evaluate the impact on some of the associated events. Microinjection of either one of the Ca2+ chelators into unactivated eggs prevented egg activation without, however, lowering [Ca2+]i, suggesting that only physiological [Ca2+]i changes, but not [Ca2+]i levels, were affected by the Ca2+ buffer. When BAPTA was microinjected around the time of occurrence of the Ca2+ transient, the egg activation-associated increase in intracellular pH (pHi) was clearly delayed. That delay was not due to a general slowing down of the cell cycle, since under the same conditions of microinjection of BAPTA the kinetics of MPF (a universal M-phase promoting factor) inactivation were unaffected. These results represent the first indication that the Ca2+ transient participates in determining the time of initiation of the pHi increase during Xenopus egg activation. The present results also demonstrate that the egg activation-associated pHi changes (a slight, transient decrease in pHi followed by a permanent increase in pHi) proceed as a wave propagating from the site of triggering of egg activation. Experiments of local microinjection of BAPTA support the view that the pH wave is a consequence of the Ca2+ wave, which it follows closely.

Kinetics of Ferrite Transformation in HSLA Steels

1988 ◽  
Vol 79 (3) ◽  
pp. 180-188
Author(s):  
Alok Singh ◽  
Durlu Ramakrishna ◽  
Shant Prakash Gupta
Keyword(s):  
Ferrite Transformation ◽  
Hsla Steels ◽  
Kinetics Of

scholarly journals High-Temperature Deformation Behavior and Microstructural Characterization of Ti-35421 Titanium Alloy

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3623 ◽  
Author(s):  
Danying Zhou ◽  
Hua Gao ◽  
Yanhua Guo ◽  
Ying Wang ◽  
Yuecheng Dong ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Deformation Temperature ◽  
Phase Region ◽  
Temperature Deformation ◽  
Β Phase ◽  
Α Phase

A self-designed Ti-35421 (Ti-3Al-5Mo-4Cr-2Zr-1Fe wt%) titanium alloy is a new type of low-cost high strength titanium alloy. In order to understand the hot deformation behavior of Ti-35421 alloy, isothermal compression tests were carried out under a deformation temperature range of 750–930 °C with a strain rate range of 0.01–10 s−1 in this study. Electron backscatter diffraction (EBSD) was used to characterize the microstructure prior to and post hot deformation. The results show that the stress–strain curves have obvious yielding behavior at a high strain rate (>0.1 s−1). As the deformation temperature increases and the strain rate decreases, the α phase content gradually decreases in the α + β phase region. Meanwhile, spheroidization and precipitation of α phase are prone to occur in the α + β phase region. From the EBSD analysis, the volume fraction of recrystallized grains was very low, so dynamic recovery (DRV) is the dominant deformation mechanism of Ti-35421 alloy. In addition to DRV, Ti-35421 alloy is more likely to occur in continuous dynamic recrystallization (CDRX) than discontinuous dynamic recrystallization (DDRX).

scholarly journals Hot Deformation Behavior and Microstructure Evolution of Cu–Ni–Co–Si Alloys

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2042 ◽  
Author(s):  
Feng Liu ◽  
Jimiao Ma ◽  
Lijun Peng ◽  
Guojie Huang ◽  
Wenjing Zhang ◽  
...  
Keyword(s):  
Strain Rate ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Strain Rate Range ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Hot Deformation Behavior ◽  
Deformation Activation Energy ◽  
The Matrix ◽  
Dynamic Recrystallization Behavior

The Cu-1.7Ni-1.4Co-0.65Si (wt%) alloy is hot compressed by a Gleeble-1500D machine under a temperature range of 760 to 970 °C and a strain rate range of 0.01 to 10 s−1. The flow stress increases with the extension of strain rate and decreases with the rising of deformation temperature. The dynamic recrystallization behavior happens during the hot compression deformation process. The hot deformation activation energy of the alloy can be calculated as 468.5 kJ/mol, and the high temperature deformation constitutive equation is confirmed. The hot processing map of the alloy is established on the basis of hot deformation behavior and hot working characteristics. With the optimal thermal deformation conditions of 940 to 970 °C and 0.01 to 10 s−1, the fine equiaxed grain and no holes are found in the matrix, which can provide significant guidance for hot deformation processing technology of Cu–Ni–Co–Si alloy.

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