scholarly journals Liquid Phase Assisted Superplastic Deformation of TiO2-Doped ZTA Ceramics

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2050 ◽  
Author(s):  
Yufei Zu ◽  
Guoqing Chen ◽  
Xuesong Fu ◽  
Wenlong Zhou
Keyword(s):  
Activation Energy ◽  
Liquid Phase ◽  
Grain Boundary ◽  
Microstructure Evolution ◽  
Deformation Behavior ◽  
Superplastic Deformation ◽  
Q Value ◽  
Deformation Activation Energy ◽  
Zirconia Toughened Alumina ◽  
Q Values

In this study, the compressive deformation of zirconia toughened alumina (ZTA) ceramics doped with different amounts of TiO2 dopants were investigated in the temperature range of 1300–1400 °C to evaluate the stress exponent (n value) and apparent deformation activation energy (Q value). With 0–8 wt.% TiO2 dopants, the n values and Q values of the TiO2-doped ZTA ceramics were calculated as 2–3 and 605–749 kJ/mol, respectively. Moreover, three grain boundary features were observed in these deformed materials, named the clean grain boundary, thin liquid phase grain boundary, and thick liquid phase grain boundary. Based on the deformation behavior and microstructure evolution, it was found that the lower apparent activation energy and higher strain rate of TiO2-doped ZTA ceramics are intensively related to the grain boundary feature.

Superplastic Deformation Behavior in Dual-Phase Mg-Ca Alloy

2016 ◽  
Vol 838-839 ◽  
pp. 256-260
Author(s):  
Takahiko Yano ◽  
Naoko Ikeo ◽  
Hiroyuki Watanabe ◽  
Toshiji Mukai
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Deformation Behavior ◽  
Superplastic Deformation ◽  
Boundary Diffusion ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Dual Phase ◽  
Elongation To Failure ◽  
Boundary Sliding

Superplastic deformation behavior was investigated for a dual-phase Mg-Ca alloy. The elongation-to-failure reached more than 120% with the strain rate sensitivity, m, over 0.4. The activation energy required for the deformation was estimated to be 98 kJ/mol which is close to the activation energy for grain boundary diffusion in magnesium. Therefore, the superplastic deformation mechanism was suggested to be the grain boundary sliding rate, which is controlled by boundary diffusion.

The Activation Energy of Superplastic Flow above the Critical Temperature for Steel CrWMn

2007 ◽  
Vol 551-552 ◽  
pp. 341-345
Author(s):  
J.B. Wen ◽  
F.X. Chen ◽  
Ke Ke Zhang ◽  
Yong Shun Yang
Keyword(s):  
Activation Energy ◽  
Critical Temperature ◽  
Grain Boundary ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Diffusion Activation Energy ◽  
Sensitivity Index ◽  
Deformation Activation Energy

By means of superplastic tensile test above the Ac1 temperature (γ→α transformation temperature), superplastic deformation activation energy of ultrafine-grained commercial die steel CrWMn is investigated on the basis of the Arrhenius theory equation, exp( / ) 1 ε& = Aσ m −Q RT , which indicates the resistance of the superplastic deformation. According to the Arrhenius equation, the activation energy is estimated from the log σt vs 1/T relationship at a constant of sensitivity index of strain rate. The results show that the strain rate sensitivity index is a constant and rather high at the conditions of superplastic deformation for the CrWMn steel, the activation energy for superplastic deformation of steel CrWMn above the critical temperature is 187KJ/mol, and the superplastic deformation activation energy is approached to the grain boundary diffusion activation energy of γ-Fe. This indicates that the grain boundary sliding (GBS) in superplastic deformation of CrWMn steel is controlled by grain boundary diffusion. The characters of superplastic deformation of the steel above the critical temperature, on the other hand, are also analyzed in this paper.

Investigation on Zener-Hollomon Parameter in the Hot Compressive Deformation Behavior of SWRCH 35K

2013 ◽  
Vol 753-755 ◽  
pp. 241-244
Author(s):  
Peng Tian ◽  
Zhi Yong Zhong ◽  
Wei Jun Hui ◽  
Rui Guo Bai ◽  
Xing Li Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Deformation Rate ◽  
Deformation Temperature ◽  
Compressive Deformation ◽  
Stored Energy ◽  
Hollomon Parameter ◽  
Deformation Activation Energy ◽  
Quadratic Fitting

The hot compressive deformation behavior of SWRCH 35K was studied with uniaxial hot compression simulation tests at 923 ~ 1223 K and strain rate of 0.01 ~ 20 /s. The results show that the hot compressive deformation activation energy was 408 kJ/mol and the rang of deformation stored energy was 10 ~ 50 J/mol. The quadratic fitting expression between deformation stored energy and Zener-Hollomon parameter (Z) was established and the deformation stored energy was considered to increased with increasing Z or with lower deformation temperature and increasing deformation rate.

Thickness of grain-boundary liquid phase and its effect on the mechanism of superplastic deformation

2011 ◽  
Vol 112 (5) ◽  
pp. 526-533 ◽  
Author(s):  
V. V. Bryukhovetskii ◽  
A. V. Poida ◽  
V. P. Poida ◽  
Yu. V. Kolomak
Keyword(s):  
Liquid Phase ◽  
Grain Boundary ◽  
Superplastic Deformation

Hot Deformation Behavior of a New-Generation 980 MPa Grade TRIP Steel for Automobiles

2011 ◽  
Vol 261-263 ◽  
pp. 775-779 ◽  
Author(s):  
Xiao Ying Hou ◽  
Yun Bo Xu ◽  
Di Wu
Keyword(s):  
Activation Energy ◽  
Regression Analysis ◽  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Trip Steel ◽  
Deformation Behavior ◽  
Critical Stress ◽  
Hot Deformation Behavior ◽  
Deformation Activation Energy ◽  
New Generation

Using a Gleeble 1500 thermo-mechanical simulator, the behavior of the dynamic recrystallization (DRX) of a low-silicon TRIP steel containing phosphorus and vanadium for automobiles is studied systematically. By the analysis of ture stress-strain curves, critical stress(σc) and strain(εc) are determined at different deformation conditions. The deformation activation energy Qdef is 323 kJ/mol. The ratios of εc/εp and σc/σp of the tested TRIP steel are 0.553 and 0.89, respectively. The equation for describing the Zener–Hollomn formula for tested steel is derived. A linear equation between σc, σp, εc, εp and lnZ have been established through regression analysis, respectively.

scholarly journals Flow Stress and Hot Deformation Activation Energy of 6082 Aluminium Alloy Influenced by Initial Structural State

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1248 ◽  
Author(s):  
Ivo Schindler ◽  
Petr Kawulok ◽  
Vladivoj Očenášek ◽  
Petr Opěla ◽  
Rostislav Kawulok ◽  
...  
Keyword(s):  
Activation Energy ◽  
Flow Stress ◽  
Strain Rate ◽  
Aluminium Alloy ◽  
Hot Deformation ◽  
True Strain ◽  
Initial Structure ◽  
Compression Tests ◽  
Deformation Activation Energy ◽  
Q Values

Stress-strain curves of the EN AW 6082 aluminium alloy with 1.2 Si-0.51 Mg-0.75 Mn (wt.%) were determined by the uniaxial compression tests at temperatures of 450–550 °C with a strain rate of 0.5–10 s−1. The initial structure state corresponded to three processing types: as-cast structure non-homogenized or homogenized at 500 °C, and the structure after homogenization and hot extrusion. Significantly higher flow stress appeared as a result of low temperature forming of the non-homogenized material. Hot deformation activation energy Q-values varied between 99 and 122 kJ·mol−1 for both homogenized materials and from 200 to 216 kJ·mol−1 for the as-cast state, while the Q-values calculated from the measured steady-state stress were always higher than those calculated from the peak stress values. For the extruded state of the 6082 alloy, the physically-based model was developed to reliably predict the flow stress influenced by dynamic softening, temperature, strain rate, and true strain up to 0.6.

scholarly journals Superplastic Deformation and Dynamic Recrystallization of a Novel Disc Superalloy GH4151

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3667 ◽  
Author(s):  
Shaomin Lv ◽  
Chonglin Jia ◽  
Xinbo He ◽  
Zhipeng Wan ◽  
Xinxu Li ◽  
...  
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
Optical Microscope ◽  
Grain Boundary Sliding ◽  
Experimental Conditions ◽  
Average Activation Energy ◽  
Boundary Sliding

The superplastic deformation of a hot-extruded GH4151 billet was investigated by means of tensile tests with the strain rates of 10−4 s−1, 5 × 10−4 s−1 and 10−3 s−1 and at temperatures at 1060 °C, 1080 °C and 1100 °C. The superplastic deformation of the GH4151 alloy was reported here for the first time. The results reveal that the uniform fine-grained GH4151 alloy exhibited an excellent superplasticity and high strain rate sensitivity (exceeded 0.5) under all experimental conditions. It was found that the increase of strain rate resulted in an increased average activation energy for superplastic deformation. A maximum elongation of 760.4% was determined at a temperature of 1080 °C and strain rate of 10−3 s−1. The average activation energy under different conditions suggested that the superplastic deformation with 1 × 10−4 s−1 in this experiment is mainly deemed as the grain boundary sliding controlled by grain boundary diffusion. However, with a higher stain rate of 5 × 10−4 s−1 and 1 × 10−3 s−1, the superplastic deformation is considered to be grain boundary sliding controlled by lattice diffusion. Based on the systematically microstructural examination using optical microscope (OM), SEM, electron backscatter diffraction (EBSD) and TEM techniques, the failure and dynamic recrystallization (DRX) nucleation mechanisms were proposed. The dominant nucleation mechanism of dynamic recrystallization (DRX) is the bulging of original grain boundaries, which is the typical feature of discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX) is merely an assistant mechanism of DRX. The main contributions of DRX on superplasticity elongation were derived from its grain refinement process.

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