Critical Condition of Dynamic Recrystallization of IN690 Using Strain Hardening Rate

2011 ◽  
Vol 148-149 ◽  
pp. 1141-1144
Author(s):  
Zhong Tang Wang ◽  
Yong Gang Deng ◽  
Shi Hong Zhang ◽  
Ming Cheng
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Hardening ◽  
Critical Strain ◽  
Critical Conditions ◽  
Peak Strain ◽  
Deformation Properties ◽  
Strain Model ◽  
Strain Hardening Rate ◽  
Super Alloy ◽  
Good Agreement

It had been studied that thermal deformation properties of super-alloy Inconel690(IN690) by thermal simulation on Gleeble 3800 Simulator, which the ranges of temperature was 1000～1200°Cand strain rates was 1.0～80/s. According to the experiment data, the critical conditions of super-alloy Inconel690 had been researched by strain hardening rate. Zener-Hollomn parameters (Z) had been introduced into establish the critical conditions of dynamic recrystallization, such as critical strain and critical stress and peak strain. The results showed that the critical strain model which established using strain hardening rate was in good agreement with that of Sellar’s model.

Effects of Anisotropy on the Microstructural Characteristics and Mechanical Behavior of Shock-Loaded of AZ31 Alloy

2011 ◽  
Vol 284-286 ◽  
pp. 1537-1541 ◽  
Author(s):  
Min Hao ◽  
Fan Zhang ◽  
Cheng Wen Tan ◽  
Tie Jian Su ◽  
Xiao Dong Yu
Keyword(s):  
Mechanical Behavior ◽  
Strain Hardening ◽  
Electron Backscatter Diffraction ◽  
Az31 Alloy ◽  
Peak Strain ◽  
Compression Tests ◽  
Microstructural Characteristics ◽  
Post Shock ◽  
Backscatter Diffraction ◽  
Strain Hardening Rate

Effects of anisotropy on the microstructural characteristics and mechanical behavior of shock loaded of AZ31 magnesium alloy have been investigated. Using electron backscatter diffraction, tension twinning was observed in both shock loading directions along the normal (ND) and rolling directions (RD). Compression tests were carried out along ND and RD in both as-received and post-shock conditions. It indicated that the RD samples show a more notable hardening behavior compared to the as-received conditions. Moreover, it is postulated here that detwinningresults in a drop of strain-hardening rate for the ND samples under post shock reload conditions and tension twinning formed during the shock wave loading process leads to a significant moving left of the peak strain hardening rate for the RD samples under post shock reload conditions.

Critical Strain Model of Cr4 Steel for Heavy Supporting Roller

2011 ◽  
Vol 117-119 ◽  
pp. 1770-1773
Author(s):  
Xue Wen Chen ◽  
Qi Zhang
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Deformation Temperature ◽  
Critical Strain ◽  
Hot Forging ◽  
Forming Process ◽  
Supporting Roller ◽  
The Mathematical Model ◽  
Strain Model ◽  
Hot Forging Process

Critical strain is the basis to determine whether the dynamic recrystallization occurs during hot deformation process, it is important for designers to control hot forming process and microstructure of final product. In order to investigate the influence of deformation temperature and strain rate on critical strain of Cr4 steel, hot compression simulation experiment was conducted for Cr4 steel in the temperature range of 750～1200°C and strain rate of 0.002～5S-1 by means of Gleeble−1500D thermo-simulation machine. The results showed that the critical strain increase with decreasing deformation temperature and increasing strain rate. Based on the experimental data and regression analysis method, the mathematical model of the critical strain of Cr4 steel is constructed. The critical strain model provides data support to predict the dynamic recrystallization during Cr4 heavy supporting roller hot forging process.

Dynamic Recrystallization and Microstructure Evolution in AZ31 Magnesium Alloy during Thermomechanical Processing

2005 ◽  
Vol 488-489 ◽  
pp. 215-218 ◽  
Author(s):  
Guang Jie Huang ◽  
Ling Yun Wang ◽  
Guang Sheng Huang ◽  
Fu Sheng Pan
Keyword(s):  
Flow Stress ◽  
Magnesium Alloy ◽  
Dynamic Recrystallization ◽  
High Temperatures ◽  
Critical Strain ◽  
Thermomechanical Processing ◽  
Stable State ◽  
Az31 Magnesium Alloy ◽  
Strain Rates ◽  
Peak Strain

The deformation behavior of AZ31 magnesium alloy has been investigated by isothermal compression at temperatures between 573-723K and at constant strain rates ranging from 10-3 -1s-1. It is shown that the form of flow stress curves is very sensitive to temperature and strain rate. In the experimental domain studied, the flow stresses are modeled using a power law with an average activation energy of 145.16 kJ/mol, and dynamic recrystallization (DRX) occurs. The critical strain for DRX is determined by analysis of flow stress curves. The ratio of the critical strain to the peak strain falls in the range of 0.4-0.5. At low temperatures and high strai rates, the deformation become macroscopically inhomogeneous, and the fracture of the specimens is accompanied by shear banding. Grain refinement resulting from DRX is less effective at high temperatures due to rapid grain growth. It is also shown that there is no difference between peak stress and stable state stress at high temperatures and lower strain rates, presenting the feature of continuous dynamic recrystallization (CDRX).

Constitutive Relationship and Critical Condition for Dynamic Recrystallization of Inconel 625 during Hot Deformation

2012 ◽  
Vol 538-541 ◽  
pp. 1240-1244 ◽  
Author(s):  
Sheng Li Guo ◽  
De Fu Li ◽  
Zhi Gang Wu
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Critical Condition ◽  
Strain Rate Range ◽  
Constitutive Relationship ◽  
Inconel 625 ◽  
Compression Tests ◽  
Order Polynomial ◽  
Strain Hardening Rate ◽  
Good Agreement

Hot compression tests of the commercial Inconel 625 were performed in the temperature range of 950 - 1200 °C and strain rate range of 0.01 - 10 s-1. The constitutive relationship and the critical condition for dynamic recrystallization of Inconel 625 were established. The influence of strain on the flow stress was investigated by considering the effect of the strain on material constants. It was found that a five-order polynomial was suitable to represent the influence of the strain. The stress-strain curves obtained by the proposed constitutive equation showed a good agreement with experimental results. It can be used for the analysis problem of hot forming processes.The critical condition for dynamic recrystallization was obtained by using strain hardening rate. The critical strain increased with temperature decreasing and strain rate increasing. The critical condition for dynamic recrystallization can be expressed as .

A Study on Dynamic Recrystallization Kinetics Model of 45Cr4NiMoV

2015 ◽  
Vol 789-790 ◽  
pp. 160-164
Author(s):  
Dae Hwan Yoon ◽  
Ya Zhang ◽  
Dong Won Jung
Keyword(s):  
Dynamic Recrystallization ◽  
Critical Condition ◽  
Critical Strain ◽  
Inflection Point ◽  
Kinetics Model ◽  
Recrystallization Kinetics ◽  
Minimum Value ◽  
Strain Model

The dynamic recrystallization critical strain of this alloy was investigated by Poliak and other scholars using the hardening rate (θ) method; they thought the critical condition corresponded to the inflection point of the lnθ-ε curve and the minimum value on the ∂ (lnθ)/∂ε-ε curve. A dynamic recrystallization critical strain model of 45Cr4NiMoV was established.

Critical Strain for the Initiation of Dynamic Recrystallization in a Fe-Cr-Ni Super Austenitic Stainless Steel

2014 ◽  
Vol 952 ◽  
pp. 130-136
Author(s):  
Chao Bei Hu ◽  
Bao Feng Guo ◽  
Yong Tao Zhang ◽  
Miao Jin ◽  
Ming Fang Ma ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Hardening ◽  
Critical Stress ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Peak Stress ◽  
Order Equation ◽  
Third Order ◽  
Super Austenitic Stainless Steel ◽  
Strain Hardening Rate

In constant strain rate tests, the occurrence of dynamic recrystallization (DRX) is traditionally identified from the presence of stress peaks in flow curves. However, not all materials display well-defined peaks when tested under these conditions. It is shown that the onset of DRX can also be identified from the inflection point on the strain hardening rate (θ=dσ/dε)versus flow stress (σ) curve. In this paper, the hot compression curves can be described by an equation that fits the experimental θ-σ data from zero to the peak stress. An appropriate third order equation was fitted to the strain hardening data. The results show that the critical stress at initiation σc=-B/3A where A and B are coefficients of the third order equation. It is evident that this value depends on the deformation conditions. The stress–strain curve was then normalized with respect to the peak stress, leading to a normalized value of the critical stress (uc) equal to uc=σc/σp=-B'/3A'. Here A'and B'are coefficients of the normalized third order equation. This value is constant and independent of the deformation conditions.

Modeling and Finite Element Analysis for the Dynamic Recrystallization Behavior of Ti-5Al-5Mo-5V-3Cr-1Zr Near β Titanium Alloy During Hot Deformation

2018 ◽  
Vol 37 (5) ◽  
pp. 445-454 ◽  
Author(s):  
Ya-ping Lv ◽  
Shao-jun Li ◽  
Xiao-yong Zhang ◽  
Zhi-you Li ◽  
Ke-chao Zhou
Keyword(s):  
Finite Element ◽  
Titanium Alloy ◽  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Critical Strain ◽  
Volume Fraction ◽  
Peak Strain ◽  
Simulation Experiments ◽  
Relationship Of ◽  
The Relationship

AbstractEvolution for the dynamic recrystallization (DRX) volume fraction of Ti-5Al-5Mo-5V-3Cr-1Zr near β titanium alloy during hot deformation was characterized by using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation. To determine the equation parameters, a series of thermal simulation experiments at the temperature of 1023–1098 K and strain rate of 0.001–1 s‒1 to the true strain of 0.7 were conducted to obtain the essential data about stress σ and strain ε. By further transforming the relationship of σ versus ε into the relationship of strain hardening rate dσ/dε versus σ, two characteristic strains at the beginning of DRX (critical strain εc) and at the peak stress (peak strain εp) were identified from the dσ/dε-σ curves. Sequentially, the parameters in the JMAK equation were determined from the linear fitting of the different relationships among critical strain εc, peak strain εp and deformation conditions (including temperature T, strain rate $\dot \varepsilon $ and strain ε). The as-obtained JMAK equation was expressed as XDRX=1-exp[-0.0053((ε-εc)/εc)2.1], where εc=0.6053εp and εp=0.0031$\dot \varepsilon $0.0081exp(28,781/RT). Finally, the JMAK equation was implanted into finite element program to simulate the hot compression of thermal simulation experiments. The simulation predictions and experimental results about the DRX volume fraction distribution showed a good consistency.

scholarly journals CONSTITUTIVE MODELING OF DYNAMIC RECRYSTALLIZATION AND PRECIPITATION BEHAVIOR OF Nb AND Ti OF Q1030 HIGH STRENGTH STEEL

2020 ◽  
Vol 1 (1) ◽  
pp. 01-05
Author(s):  
J.J. Wang ◽  
Y.L. Kang ◽  
Y.L. Liu ◽  
H Yu
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
High Strength Steel ◽  
Critical Strain ◽  
High Strength ◽  
Second Phase ◽  
Peak Strain ◽  
Precipitation Behavior ◽  
Deformation Equation

The thermal deformation and precipitation behavior at 900-1100℃ and strain rate of 0.1-5s-1 were studied by Gleeble-3800 thermal simulator of Q1030 high strength steel. The activation energy of hot deformation in austenite region was determined by regression method, and the hot deformation equation of the Q1030 high strength steel was established. The critical strain and peak strain of dynamic recrystallization were predicted accurately by fitting the inflection point with cubic polynomial of curve of Q1030 high strength steel, and relationship between critical strain and Z parameter was established. Finally, the precipitation behavior of Nb and Ti particles during low strain rate deformation was studied, the results show that the precipitated phases in steel are rectangular TiN, quadratic (Nb, Ti) (C, N) carbonitride, elliptical (Nb, Ti) C carbide and NbC. Thermodynamic calculation shows that the order of precipitation of the second phase in steel is TiN, TiC, NbC and NbN.

scholarly journals Hot Compression Behavior of New Al-6Mg and Al-8Mg Alloy with Improved Hot Workability Fabricated by Direct Chill Casting Method

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 288
Author(s):  
Nam-Seok Kim ◽  
Kweon-Hoon Choi ◽  
Seung-Yoon Yang ◽  
Seong-Ho Ha ◽  
Young-Ok Yoon ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Compression Test ◽  
Deformation Behavior ◽  
Hot Compression ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strength Increase ◽  
Peak Strain ◽  
Hot Workability ◽  
Hot Compression Test

A hot compression test of new Al-6Mg and Al-8Mg alloys was conducted to understand the dynamic recrystallization (DRX) behavior by Mg contents. To investigate the hot workability of Al-Mg with high Mg contents, the hot deformation behavior of Al-6Mg and Al-8Mg alloys was analyzed by a hot compression test in the temperature range of 300–450 °C, and the strain rate range of 10−3–100/s. Subsequently, high-temperature deformation behavior was investigated through the processing map and microstructure observation. In this study, the results have shown that, as the Mg contents increase, the maximum and yield strength increase while rapid flow softening after the peak strain has been observed due to accelerated dynamic recrystallization (DRX). Finally, the increase of Mg contents affects an increase of heat dissipation efficiency to be an indicator of regular deformation.

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