The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Qing Liu - One of the best experts on this subject based on the ideXlab platform.
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Inhomogeneous Deformation of 111 grain in cold rolled tantalum
Journal of Materials Science & Technology, 2018Co-Authors: Yahui Liu, Shifeng Liu, Chao Deng, Haiyang Fan, Xiaoli Yuan, Qing LiuAbstract:Abstract The microstructures of {111} grain were characterized in detailed and systematically investigated with the aid of electron backscatter diffraction (EBSD) and transmission electron microscope (TEM). The stored energy in different regions in the grain was evaluated by the band contrast values collected from EBSD. The results show that the distribution of energy is Inhomogeneous through the grain. Especially, the regions containing the least and the largest energy were extracted from the EBSD data, and then quantitatively analyzed based on the misorientation and Schmid factor. Many peaks with large misorientation appeared in the region containing larger energy, and these peaks represent the existences of micro-bands and micro-shear bands in {111} grain. The results of Schmid factor suggest that the region containing larger energy is prone to deforming ahead of the region with less stored energy, implying the more serious subdivision of the microstructure of region with larger stored energy.
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Inhomogeneous Deformation of {111} grain in cold rolled tantalum
Journal of Materials Science & Technology, 2018Co-Authors: Yahui Liu, Shifeng Liu, Chao Deng, Haiyang Fan, Xiaoli Yuan, Qing LiuAbstract:Abstract The microstructures of {111} grain were characterized in detailed and systematically investigated with the aid of electron backscatter diffraction (EBSD) and transmission electron microscope (TEM). The stored energy in different regions in the grain was evaluated by the band contrast values collected from EBSD. The results show that the distribution of energy is Inhomogeneous through the grain. Especially, the regions containing the least and the largest energy were extracted from the EBSD data, and then quantitatively analyzed based on the misorientation and Schmid factor. Many peaks with large misorientation appeared in the region containing larger energy, and these peaks represent the existences of micro-bands and micro-shear bands in {111} grain. The results of Schmid factor suggest that the region containing larger energy is prone to deforming ahead of the region with less stored energy, implying the more serious subdivision of the microstructure of region with larger stored energy.
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mechanisms of fracture and Inhomogeneous Deformation on transverse tensile test of friction stir processed az31 mg alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: Renlong Xin, Dejia Liu, Liyun Sun, Zheng Zhou, Qing LiuAbstract:Abstract Three kinds of AZ31 plates with different initial grain orientations were friction stir processed (FSP). Detailed microstructure and texture evolutions of the FSP plates were obtained. Fracture behavior and non-uniform plastic Deformation were focused on. It was found that initial grain orientation had little effect on grain size and texture evolution in stir zone (SZ), but it greatly affected the texture transition at thermal–mechanical affected zone (TMAZ)/SZ interface. Non-uniform plastic Deformation was observed in all the three kinds of FSP plates along the tensile direction. The strength difference of the FSP plates was largely reduced compared with the initial plates. Fracture consistently initiated in transition region on advancing side even for the 90° specimen, in which no sudden texture transition was present at TMAZ/SZ interface. As revealed in electron backscatter diffraction (EBSD) maps, SZ-side could be divided into two micro-regions. One was adjacent to TMAZ/SZ interface, named as the region of easy to activate extension twinning (EAET region), where the c -axis was almost parallel with transverse direction (TD). The other was slightly away from TMAZ/SZ interface, named as the region of easy to activate basal slip (EABS region), where the c -axis was tilted about 45° towards TD. The activation of different Deformation mechanisms in SZ-side may cause plastic Deformation incompatibility and initiate fracture. An “embossed” phenomenon appeared in SZ-center during the transverse tensile tests of all the three kinds of FSP plates, which was related to the distribution of basal plane and caused by the different Deformation between SZ-center and SZ-side. The activation of basal slip in EABS region was considered as a major role in the formation of the “embossed phenomenon”. The findings of this study extend understanding the mechanism of fracture and Inhomogeneous Deformation behaviors of FSP Mg alloys.
Byungmin Kim - One of the best experts on this subject based on the ideXlab platform.
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evaluation of axial surface residual stress in 0 82 wt carbon steel wire during multi pass drawing process considering heat generation
Materials & Design, 2012Co-Authors: Sangkon Lee, Daewoon Kim, Myeongsik Jeong, Byungmin KimAbstract:Abstract In a multi-pass wire drawing process, Inhomogeneous Deformation through the cross section of a wire, heat generation resulting from plastic Deformation, and friction generate residual stress in the drawn wire. The tensile residual stress in the wire deteriorates the mechanical properties of the drawn wire, with the maximum tensile residual stress occurring on its surface. This paper proposes a prediction model for the maximum axial residual stress that considers the Inhomogeneous Deformation and heat generation in a high-carbon (0.82-wt% C) drawn wire. An elastoplastic finite element (FE) analysis that considered the flow stress at a high strain range was carried out. Based on the results of this FE analysis, a stress prediction model was established. In order to verify the effectiveness of the prediction model, a multi-pass wire drawing experiment was performed. After performing the drawing experiment, the axial surface residual stress in the drawn wire was measured by X-ray diffraction. From the results, a close agreement was observed between the predicted residual stress and the measured residual stress.
Markus Rettenmayr - One of the best experts on this subject based on the ideXlab platform.
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modelling study on recrystallization recovery and their temperature dependence in Inhomogeneously deformed materials
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2002Co-Authors: Xiaoyan Song, Markus RettenmayrAbstract:A hybrid analytical/Monte Carlo model is set up for studying recovery and recrystallization at various annealing temperatures after Inhomogeneous Deformation. Equations are derived to describe the nucleation rate and the evolution of the stored energy as functions of local Deformation, temperature and time. The analytical equations and a description of the Inhomogeneous pre-Deformation are introduced into a Monte Carlo model. The microstructure evolution is simulated for various temperatures and times. The characteristics of recrystallization after Inhomogeneous Deformation and the interaction between recrystallization and recovery are well reproduced and generated by the model. Due to the Inhomogeneous pre-Deformation, the recrystallized fraction varies strongly depending on the given processing conditions. The simulation calculations agree well with experiments for both morphological features and quantitative analysis.
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Modeling of recrystallization after Inhomogeneous Deformation
Metallurgical and Materials Transactions A, 2001Co-Authors: X. Song, Markus Rettenmayr, Clemens Müller, H. E. ExnerAbstract:Recrystallization in an Inhomogeneously predeformed material (a cold-drawn cylindrical rod) is described by an analytical model and simulated with the Monte-Carlo technique. For this purpose, an equation for the nucleation rate during recrystallization as a function of local Deformation has been derived. The analytical model considering the derived nucleation equation is capable of predicting the progress of the recrystallization front as observed in experiments with Titanium Grade 2. The Monte-Carlo model has been developed on the basis of the analytical model. Different functions for the local Deformation were introduced, and recrystallization and subsequent grain growth were simulated. With the aid of simulation, the formation of both a grain size gradient and large elongated grains in the region of critical Deformation can be understood. The graded microstructure is a consequence of the combined effect of Inhomogeneous nucleation and anisotropic growth of the recrystallizing grains. Experimental grain size gradients were reproduced quantitatively by the present simulations. Agreement was also found for the grain elongation that forms during the recrystallization and grain growth stages.
In Sup Kim - One of the best experts on this subject based on the ideXlab platform.
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Tensile properties and Inhomogeneous Deformation of ferrite-martensite dual-phase steels
Journal of Materials Science, 1993Co-Authors: Thak Sang Byun, In Sup KimAbstract:The tensile properties and Inhomogeneous Deformation of coarse ferrite-martensite dual-phase steels containing 17–50% martensite were analysed. The stress of dual-phase steels at equal strain increased with increasing volume fraction of martensite, f , but the rate of increase was reduced after f=0.3. The strain hardening rate was dependent on f at small strains (ɛ ⩽ 0.03), however, it became independent of f at larger strains. It was found that the Deformation of the dual-phase steels divided into three different stages when f was less than about 0.3. The concurrent in situ stress-strain states of ferrite, martensite and their composite, and the stress ratios and strain ratios between ferrite and martensite were evaluated by means of a new stress and strain partition theory. The martensite phase deformed plastically after the uniform strain for f < 0.25, while it was plastic before the uniform strain for f > 0.25. The theoretical analyses for Inhomogeneous Deformation implied that the volume-fraction dependence of the stress and the characteristics of the strain-hardening rate were influenced by the plastic Deformation of martensite. Further, the in situ stress-strain curves of ferrite and martensite and the internal stresses at respective phases were calculated from the partitioned stresses and strains.
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Tensile properties and Inhomogeneous Deformation of ferrite-martensite dual-phase steels
Journal of Materials Science, 1993Co-Authors: Thak Sang Byun, In Sup KimAbstract:The tensile properties and Inhomogeneous Deformation of coarse ferrite-martensite dual-phase steels containing 17–50% martensite were analysed. The stress of dual-phase steels at equal strain increased with increasing volume fraction of martensite, f, but the rate of increase was reduced after f=0.3. The strain hardening rate was dependent on f at small strains (ɛ ⩽ 0.03), however, it became independent of f at larger strains. It was found that the Deformation of the dual-phase steels divided into three different stages when f was less than about 0.3. The concurrent in situ stress-strain states of ferrite, martensite and their composite, and the stress ratios and strain ratios between ferrite and martensite were evaluated by means of a new stress and strain partition theory. The martensite phase deformed plastically after the uniform strain for f 0.25. The theoretical analyses for Inhomogeneous Deformation implied that the volume-fraction dependence of the stress and the characteristics of the strain-hardening rate were influenced by the plastic Deformation of martensite. Further, the in situ stress-strain curves of ferrite and martensite and the internal stresses at respective phases were calculated from the partitioned stresses and strains.
Chia-chow Keh - One of the best experts on this subject based on the ideXlab platform.
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Inhomogeneous Deformation and residual stress in skin-pass axisymmetric drawing
Journal of Materials Processing Technology, 2007Co-Authors: Heng-sheng Lin, Yuan-chuan Hsu, Chia-chow KehAbstract:Abstract Skin-pass drawing is usually conducted in the final stage of wire, rod or shaped-section drawing or shape rolling. It helps improve shape accuracy and reduce residual stress of the drawn or rolled workpieces. However, its characteristic low reduction induces large Δ-parameter, and causes significant Inhomogeneous Deformation in the workpiece. In this work, finite-element software DEFORM 2D was utilized to investigate the effect of Δ-parameter on Inhomogeneous Deformation and residual stress of mid-carbon steel through various combinations of area reduction and die semi-angle. The effect of the friction was also investigated. The results showed that the inhomogeneity factor of effective strain decreased with area reduction and increased with die semi-angle and friction. The level of Inhomogeneous Deformation could be reduced by drawing with small die semi-angle, and the influence of the friction was only substantial near the surface of the drawn workpiece. The axial and circumferential residual stresses would approach to compressive on the drawn surface in extreme light reductions.