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.

A Model for the Effects of Strain Rate and Temperature on the Deformation Behavior of Ultrafine-Grained Metals

2011 ◽  
Vol 291-294 ◽  
pp. 1173-1177
Author(s):  
Zi Ling Xie ◽  
Lin Zhu Sun ◽  
Fang Yang
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Boundary Diffusion ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Dislocation Slip ◽  
Deformation Response ◽  
Ultrafine Grained ◽  
Boundary Sliding

A theoretical model is developed to account for the effects of strain rate and temperature on the deformation behavior of ultrafine-grained fcc Cu. Three mechanisms, including dislocation slip, grain boundary diffusion, and grain boundary sliding are considered to contribute to the deformation response simultaneously. Numerical simulations show that the strain rate sensitivity increases with decreasing grain size and strain rate, and that the flow stress and tensile ductility increase with either increasing strain rate or decreasing deformation temperature.

Superplasticity in Ultrahigh Carbon (1.6 Pct C) Steel

2007 ◽  
Vol 551-552 ◽  
pp. 199-202 ◽  
Author(s):  
Zhan Ling Zhang ◽  
Yong Ning Liu ◽  
Jie Wu Zhu ◽  
G. Yu
Keyword(s):  
Grain Boundary ◽  
Superplastic Deformation ◽  
Boundary Diffusion ◽  
Grain Boundary Sliding ◽  
Strain Rates ◽  
Ultrahigh Carbon Steel ◽  
Elongation To Failure ◽  
Boundary Sliding ◽  
Dynamic Grain Growth ◽  
Microduplex Structure

Ultrahigh carbon steel containing 1.6 wt pct C was processed to create microduplex structure consisting of fine-spheroidized carbides and fine ferrite grains. Elongation-to-failure tests were conducted at strain rates from 10-4s-1 to 15×10-4s-1, and at temperatures from 600 °C to 850 °C. The steel exhibited superplasticity at and above 700 °C when testing at a strain rate of 10-4s-1, and at 800 °C when testing at strain rates of 7×10-4s-1 and slower. The grains retained the equiaxed shape and initial size during deformation; dynamic grain growth was not observed after superplastic deformation, whereas carbide coarsening was observed. It is concluded that the fine ferrite grains or austensite grains are stabilized by the grain boundary carbides, and grain-boundary sliding controlled by grain boundary diffusion is the principal superplastic deformation mechanism at temperatures in the range of 700-850 °C.

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.

Superplastic Deformation Mechanisms in High Magnesium Contenting Aluminum Alloy

2016 ◽  
Vol 838-839 ◽  
pp. 66-71 ◽  
Author(s):  
O.A. Yakovtseva ◽  
Anastasia V. Mikhaylovskaya ◽  
A.G. Mochugovskiy ◽  
V.V. Cheverikin ◽  
Vladimir K. Portnoy
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Superplastic Deformation ◽  
Effective Activation Energy ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Effective Activation ◽  
Continuous Formation ◽  
Boundary Sliding ◽  
Dynamic Grain Growth

The evolution of surface, grains and dislocation structures during superplastic deformation was studied in Al–6.8%Mg–0.6%Mn–0.25%Cr alloy by SEM, EBSD, TEM techniques. The effective activation energy of superplastic deformation was calculated. Contribution of grain boundary sliding was defined during superplastic deformation. Low value of grain boundary sliding, significant dynamic grain growth in stress direction, high dislocations activity and permanent continuous formation of sub-grain boundaries during superplastic deformation were found.

Superplastic Deformation Mechanisms in a Fine-Grained, Yttria-stabilized Tetragonal Zirconia Polycrystal (Y-TZP)

1990 ◽  
Vol 196 ◽  
Author(s):  
T. G. Nieh ◽  
J. Wadsworth
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Grain Growth ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Boundary Triple ◽  
Sliding Mechanism ◽  
Boundary Sliding

ABSTRACTConcurrent grain growth, and in particular, dynamic grain growth, was observed to take place during superplastic deformation of Y-TZP. As a result of this concurrent grain growth, the measured strain rate sensitivity was found to be lower than that measured under constantstructure conditions. In the present paper, data obtained from the superplastic deformation of YTZP under constant-structure conditions are presented. It is demonstrated that the strain rate sensitivity values are generally higher than 0.5, when measured from the grain size-compensated data; this result suggests a grain boundary sliding mechanism. Microstructures from samples prior to and after superplastic deformation reveal grains which are essentially equiaxed; this observation is also consistent with a grain boundary sliding mechanism. Both high-resolution images of grain boundary triple points using transmission electron microscopy, and fracture surface studies using Auger electron spectroscopy and X-ray photoelectron spectroscopy indicate that there is no evidence for the presence of glassy phases at grain boundaries in Y-TZP.

scholarly journals Superplastic behavior of a fine-grained Mg–9Li material at low homologous temperature

1992 ◽  
Vol 7 (8) ◽  
pp. 2131-2135 ◽  
Author(s):  
Eric M. Taleff ◽  
Oscar A. Ruano ◽  
Jeff Wolfenstine ◽  
Oleg D. Sherby
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Strain Rate ◽  
Boundary Diffusion ◽  
Rate Sensitivity ◽  
Superplastic Behavior ◽  
Homologous Temperature ◽  
Fine Grained ◽  
Processed Material ◽  
Elongation To Failure

A fine-grained ($\overline \iota$m) laminate containing 91.0 wt.% magnesium and 9.0 wt. % lithium was prepared by a foil metallurgy technique involving rolling and pressing at low homologous temperature (0.39–0.49 Tm). The processed material exhibits superplastic characteristics above 70 °C (0.40 Tm). The strain-rate-sensitivity exponent is about 0.5 and an elongation-to-failure of 450% was obtained at 100 °C (0.43 Tm). The activation energy for plastic flow in the superplastic region is 65 kJ/mole. This value of the activation energy is related to the expected activation energy for grain boundary diffusion.

A Comparative Study on Superplasticity of Mg-Zn-Y-Zr Processed by ECAE and Hot Rolling

2007 ◽  
Vol 551-552 ◽  
pp. 203-208 ◽  
Author(s):  
Wei Neng Tang ◽  
Hong Yan ◽  
Rong Shi Chen ◽  
En Hou Han
Keyword(s):  
Hot Rolling ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Sensitivity Coefficient ◽  
Grain Boundary Sliding ◽  
Diffusional Creep ◽  
Dislocation Creep ◽  
Fine Grained ◽  
Microstructure Observation ◽  
Elongation To Failure

Superplastic deformation (SPD) behaviors of two fine-grained materials produced by ECAE and hot rolling methods have been contrastively studied in this paper. It is found that the optimum superplastic condition in as-ECAEed material was at 350°C and 1.7×10-3s-1 with elongation to failure about 800%; while in as-rolled material, the largest elongation to failure about 1000% was obtained at 480°C and 5.02×10-4s-1. Microstructure observation showed that grain evolution and cavitation behavior were different in these two materials during superplastic deformation. The controlled mechanisms for superplasticity, i.e. grain boundary sliding (GBS), dislocation creep and diffusional creep, at different deformation conditions were discussed in terms of strain rate sensitivity coefficient, stress exponent and activity energy.

scholarly journals Deformation Behavior of Nanocrystalline Body-Centered Cubic Iron with Segregated, Foreign Interstitial: A Molecular Dynamics Study

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5351
Author(s):  
Ahmed Tamer AlMotasem ◽  
Matthias Posselt ◽  
Tomas Polcar
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Deformation Behavior ◽  
Large Scale ◽  
Grain Boundary Sliding ◽  
Carbon And Nitrogen ◽  
Embedded Atom ◽  
Boundary Sliding ◽  
Dynamics Simulations

In the present work, modified embedded atom potential and large-scale molecular dynamics’ simulations were used to explore the effect of grain boundary (GB) segregated foreign interstitials on the deformation behavior of nanocrystalline (nc) iron. As a case study, carbon and nitrogen (about 2.5 at.%) were added to (nc) iron. The tensile test results showed that, at the onset of plasticity, grain boundary sliding mediated was dominated, whereas both dislocations and twinning were prevailing deformation mechanisms at high strain. Adding C/N into GBs reduces the free excess volume and consequently increases resistance to GB sliding. In agreement with experiments, the flow stress increased due to the presence of carbon or nitrogen and carbon had the stronger impact. Additionally, the simulation results revealed that GB reduction and suppressing GBs’ dislocation were the primary cause for GB strengthening. Moreover, we also found that the stress required for both intragranular dislocation and twinning nucleation were strongly dependent on the solute type.

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