The Experts below are selected from a list of 32196 Experts worldwide ranked by ideXlab platform
Terence G Langdon - One of the best experts on this subject based on the ideXlab platform.
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Microstructural Evolution in a two phase alloy processed by high pressure torsion
Acta Materialia, 2010Co-Authors: Megumi Kawasaki, Terence G Langdon, Byungmin AhnAbstract:Abstract Experiments were conducted to evaluate the Microstructural Evolution occurring in the Zn–22% Al eutectoid alloy when processed by high-pressure torsion (HPT) over a range of experimental conditions. Processing by HPT reduces the grain size and at the edges of the disks it produces agglomerates of Zn-rich and Al-rich grains lying in bands delineating the torsional straining. Unlike most metals processed by HPT, the measured hardness values are lower than in the initial annealed condition. This is due to a significant reduction during processing in the distribution of Zn precipitates which are visible within the Al-rich grains in the annealed condition. It is shown that all of the hardness measurements are mutually consistent when plotted against the calculated equivalent strain.
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experimental parameters influencing grain refinement and Microstructural Evolution during high pressure torsion
Acta Materialia, 2003Co-Authors: Alexander P Zhilyaev, G V Nurislamova, B K Kim, M D Baro, J A Szpunar, Terence G LangdonAbstract:Abstract Pure nickel was selected for a detailed investigation of the experimental parameters influencing grain refinement and Microstructural Evolution during processing by high-pressure torsion (HPT). Samples were examined after HPT using microhardness measurements, transmission electron microscopy and orientation imaging microscopy. Processing by HPT produces a grain size of ~170 nm in pure Ni, and homogeneous and equiaxed microstructures are attained throughout the samples when they are subjected to at least ~5 whole rEvolutions under applied pressures of at least ~6 GPa. For these conditions, the distributions of grain boundary misorientations are similar in the center and at the periphery of the samples. A simple model is proposed to explain the development of a homogeneous microstructure in HPT.
Z X Guo - One of the best experts on this subject based on the ideXlab platform.
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Microstructural Evolution of a ti 6al 4v alloy during β phase processing experimental and simulative investigations
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: R Ding, Z X GuoAbstract:Abstract The Microstructural Evolution of a Ti–6Al–4V alloy during thermomechanical processing in the β-phase field was investigated using both experimental and modelling methods. The experimental results show that dynamic and/or metadynamic recrystallization occurred when the alloy was processed in the β-phase field. A model embedding fundamental metallurgical principles of dynamic recrystallization (DRX) within the cellular automaton (CA) method was able to simulate quantitatively and topographically the Microstructural Evolution and the flow stress–strain relationship during the thermomechanical processing. In the simulation, the dislocation density variation and the grain growth kinetics of each dynamically recrystallizing grain (R-grain) was calculated on the physical model of DRX, and the plastic flow curve was calculated directly from the dislocation density variation of the matrix grains and the R-grains. The equiaxed growth of R-grains was simulated using the CA method. The influence of strain rate and temperature on the Microstructural Evolution and the flow stress during dynamic recrystallization was studied, and the results compared with experiments.
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coupled quantitative simulation of Microstructural Evolution and plastic flow during dynamic recrystallization
Acta Materialia, 2001Co-Authors: R Ding, Z X GuoAbstract:Abstract A new modelling approach that couples fundamental metallurgical principles of dynamical recrystallization (DRX) with the cellular automaton (CA) method has been developed to simulate the Microstructural Evolution and the plastic flow behaviour during thermomechanical processing with DRX. It provides an essential link for multiscale modelling to bridge mesostructural dislocation activities with Microstructural grain boundary dynamics, allowing accurate predictions of microstructure, plastic flow behaviour, and property attributes. Variations of dislocation density and growth kinetics of each dynamically recrystallizing grain (R-grain) were determined by metallurgical relationships of DRX, and the flow stress was evaluated from the average dislocation density of the matrix and all the R-grains. The growth direction and the shape of each R-grain were simulated using the CA method. The predictions of Microstructural Evolution and the flow behaviour at various hot working conditions agree well with the experimental results for an oxygen free high conductivity (OFHC) copper. It is identified that the oscillation of the flow stress–strain curve not only depends on thermomechanical processing parameters (strain rate and temperature) but also the initial microstructure. The mean size of R-grains is only a function of the Zener–Hollomon parameter. However, the percentage of DRX is not only related with the Zener–Hollomon parameter, but also influenced by the nucleation rate and the initial microstructure.
R Ding - One of the best experts on this subject based on the ideXlab platform.
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Microstructural Evolution of a ti 6al 4v alloy during β phase processing experimental and simulative investigations
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: R Ding, Z X GuoAbstract:Abstract The Microstructural Evolution of a Ti–6Al–4V alloy during thermomechanical processing in the β-phase field was investigated using both experimental and modelling methods. The experimental results show that dynamic and/or metadynamic recrystallization occurred when the alloy was processed in the β-phase field. A model embedding fundamental metallurgical principles of dynamic recrystallization (DRX) within the cellular automaton (CA) method was able to simulate quantitatively and topographically the Microstructural Evolution and the flow stress–strain relationship during the thermomechanical processing. In the simulation, the dislocation density variation and the grain growth kinetics of each dynamically recrystallizing grain (R-grain) was calculated on the physical model of DRX, and the plastic flow curve was calculated directly from the dislocation density variation of the matrix grains and the R-grains. The equiaxed growth of R-grains was simulated using the CA method. The influence of strain rate and temperature on the Microstructural Evolution and the flow stress during dynamic recrystallization was studied, and the results compared with experiments.
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coupled quantitative simulation of Microstructural Evolution and plastic flow during dynamic recrystallization
Acta Materialia, 2001Co-Authors: R Ding, Z X GuoAbstract:Abstract A new modelling approach that couples fundamental metallurgical principles of dynamical recrystallization (DRX) with the cellular automaton (CA) method has been developed to simulate the Microstructural Evolution and the plastic flow behaviour during thermomechanical processing with DRX. It provides an essential link for multiscale modelling to bridge mesostructural dislocation activities with Microstructural grain boundary dynamics, allowing accurate predictions of microstructure, plastic flow behaviour, and property attributes. Variations of dislocation density and growth kinetics of each dynamically recrystallizing grain (R-grain) were determined by metallurgical relationships of DRX, and the flow stress was evaluated from the average dislocation density of the matrix and all the R-grains. The growth direction and the shape of each R-grain were simulated using the CA method. The predictions of Microstructural Evolution and the flow behaviour at various hot working conditions agree well with the experimental results for an oxygen free high conductivity (OFHC) copper. It is identified that the oscillation of the flow stress–strain curve not only depends on thermomechanical processing parameters (strain rate and temperature) but also the initial microstructure. The mean size of R-grains is only a function of the Zener–Hollomon parameter. However, the percentage of DRX is not only related with the Zener–Hollomon parameter, but also influenced by the nucleation rate and the initial microstructure.
Ming-song Chen - One of the best experts on this subject based on the ideXlab platform.
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study of Microstructural Evolution during static recrystallization in a low alloy steel
Journal of Materials Science, 2009Co-Authors: Y.c. Lin, Ming-song ChenAbstract:Hot compression tests of 42CrMo steel were carried out on Gleeble-1500 thermo-mechanical simulator. The effects of forming temperature, strain rate, deformation degree, and initial austenite grain size on the Microstructural Evolution during static recrystallization in hot deformed 42CrMo steel were discussed. Based on the experimental results, the grain size model for static recrystallization was established. It is found that the effects of the processing parameters on the Microstructural Evolution during static recrystallization are significant, while those of the initial austenitic grain size are not obvious. Additionally, a good agreement between the experimental and predicted grain sizes was also obtained.
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Study of Microstructural Evolution during metadynamic recrystallization in a low-alloy steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Y.c. Lin, Ming-song ChenAbstract:Abstract Using Gleeble-1500 thermo-mechanical simulator, the Microstructural Evolutions during metadynamic recrystallization of 42CrMo steel were investigated by hot compressive deformation tests at forming temperatures of 850–1150 °C, strain rates of 0.01–1 s −1 , and initial austenite grain sizes of 54–155 μm. The effects of forming temperature, strain rate and the initial austenitic grain size on the Microstructural Evolution during metadynamic recrystallization in hot deformed 42CrMo steel were discussed in detail. Based on the experimental results, the grain size model for metadynamic recrystallization was established. It is found that the effects of forming parameters (temperature and strain rate) on the Microstructural Evolution during metadynamic recrystallization are significant, while those of the initial austenitic grain size are obvious only when the initial austenitic grain size is less than 104 μm. A good agreement between the experimental and predicted grain sizes was obtained, which verified the developed grain size model.
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numerical simulation for stress strain distribution and Microstructural Evolution in 42crmo steel during hot upsetting process
Computational Materials Science, 2008Co-Authors: Y.c. Lin, Ming-song Chen, Jue ZhongAbstract:Based on experimental results, the dynamic recrystallization mathematical models of 42CrMo steel were derived. The effects of strain rates on the strain/stress distribution and Microstructural Evolution in 42CrMo steel during hot upsetting process were simulated by integrating the thermo-mechanical coupled finite element model. The results show that the deformation of the specimen is inhomogeneous, and the degree of the deformation inhomogeneity decreases with the increase of strain rates. The distribution of the effective stress in the specimen is also inhomogeneous, and the locus of the maximum effective stress changes with the variations of strain rates. The dynamic recrystallization volume fraction decreases with the increase of strain rates. The distribution of the dynamic recrystallization grain is inhomogeneous in the deformed specimen, and the average dynamic recrystallization grain size decreases as the strain rate is increased. A good agreement between the predicted and experimental results confirmed that the derived dynamic recrystallization mathematical models can be successfully incorporated into the finite element model to predict the Microstructural Evolution in the hot upsetting process for 42CrMo steel.
Z Y - One of the best experts on this subject based on the ideXlab platform.
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Microstructural Evolution of the thermomechanically affected zone in a ti 6al 4v friction stir welded joint
Scripta Materialia, 2014Co-Authors: L H Wu, D Wang, B L Xiao, Z YAbstract:Microstructural Evolution of the thermomechanically affected zone (TMAZ) in a friction stir welded Ti–6Al–4V joint was investigated by electron backscattered diffraction and transmission electron microscopy. The TMAZ showed the lowest hardness in the friction stir welded sample. By comparing Microstructural details of the TMAZ, including texture, misorientation angle distribution and grain structure, with those of the base material, we propose a new grain refinement model associated with continuous dynamic recrystallization and grooving in the TMAZ.
