The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Saiyi Li - One of the best experts on this subject based on the ideXlab platform.
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Dependencies of grain refinement on processing route and Die Angle in equal channel angular extrusion of bcc materials
Computational Materials Science, 2009Co-Authors: Saiyi LiAbstract:Abstract The efficiency of grain refinement in equal channel angular extrusion of body-centered cubic (bcc) materials is investigated based on slip activities from crystal plasticity simulations, which account for both the macroscopic and crystallographic features of deformation. It is shown that the characteristics of slip activities, especially the relative contributions of slip systems newly activated or reversed at the transitions between successive passes, vary significantly with the processing routes (A, B and C) and Die Angles ( ϕ = 90° and 120°). The simulations assuming {1 1 0}〈111〉 slip suggest that routes B and A lead to the most significant contributions of newly activated slip systems and hence are most efficient for grain refinement with ϕ = 90° and 120°, respectively. Further incorporation of {1 1 2}〈111〉 slip systems leads to the highest efficiency by route B for both Die Angles. These predictions are in partial agreement with experimental observations in the literature. Comparison of these results with those of face-centered cubic materials reveals the relevance of crystal structure and deformation mechanism during grain refinement.
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A crystal plasticity-based explanation for the dependencies of grain refinement on processing route and Die Angle in equal channel angular extrusion
Scripta Materialia, 2009Co-Authors: Saiyi LiAbstract:An explanation for the relative effectiveness of grain refinement in equal channel angular extrusion is proposed based on crystal plasticity simulations. It is shown that the processing route and Die Angle have significant influences on the characteristics of slip activities at pass-to-pass transitions. A higher efficiency of grain refinement by the experimentally recognized optimum route is attributed to a higher contribution from newly activated slip systems at the transitions.
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microstructure and texture evolution during equal channel angular extrusion of interstitial free steel effects of Die Angle and processing route
Acta Materialia, 2007Co-Authors: Saiyi Li, Azdiar A Gazder, Irene J Beyerlein, C H J Davies, Elena V PerelomaAbstract:Abstract Die Angle ( Φ ) and processing route are two important factors that greatly impact microstructure and texture developments during equal channel angular extrusion (ECAE). In this study, the microstructure and texture evolution in interstitial-free steel during ECAE using a Φ = 120° Die are investigated for up to four passes via three routes (A, B C and C). Finite element simulations and polycrystal modeling using the Taylor and viscoplastic self-consistent models are conducted to help understand deformation behavior and texture formation. Transmission electron microscopy results reveal remarkable microstructural differences between various observation planes for each billet. The effects of Φ and processing route are discussed by comparing the current results with those for the same material processed via the same routes but using a Φ = 90° Die. The efficiency of grain refinement is found to be only mildly dependent on Φ and processing route. The textures can be completely characterized by predefined ideal fibers, regardless of processing route and pass number. With the exception of even-numbered passes in route C, textures developed after the same route and pass number, but different Φ can be approximately related by a rotation about the axis normal to the flow plane and the rotation Angle is half of the Φ difference.
Elena V Pereloma - One of the best experts on this subject based on the ideXlab platform.
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microstructure and texture evolution during equal channel angular extrusion of interstitial free steel effects of Die Angle and processing route
Acta Materialia, 2007Co-Authors: Saiyi Li, Azdiar A Gazder, Irene J Beyerlein, C H J Davies, Elena V PerelomaAbstract:Abstract Die Angle ( Φ ) and processing route are two important factors that greatly impact microstructure and texture developments during equal channel angular extrusion (ECAE). In this study, the microstructure and texture evolution in interstitial-free steel during ECAE using a Φ = 120° Die are investigated for up to four passes via three routes (A, B C and C). Finite element simulations and polycrystal modeling using the Taylor and viscoplastic self-consistent models are conducted to help understand deformation behavior and texture formation. Transmission electron microscopy results reveal remarkable microstructural differences between various observation planes for each billet. The effects of Φ and processing route are discussed by comparing the current results with those for the same material processed via the same routes but using a Φ = 90° Die. The efficiency of grain refinement is found to be only mildly dependent on Φ and processing route. The textures can be completely characterized by predefined ideal fibers, regardless of processing route and pass number. With the exception of even-numbered passes in route C, textures developed after the same route and pass number, but different Φ can be approximately related by a rotation about the axis normal to the flow plane and the rotation Angle is half of the Φ difference.
Sung Hyuk Park - One of the best experts on this subject based on the ideXlab platform.
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Die Angle dependency of microstructural inhomogeneity in an indirect extruded az31 magnesium alloy
Journal of Materials Processing Technology, 2015Co-Authors: Hui Yu, Sung Hyuk ParkAbstract:Abstract The variation induced in the microstructural inhomogeneity of AZ31 alloy subjected to indirect extrusion was stuDied using tool steel Dies with Angles of 30°, 60° and 90°. Finite element modeling (FEM) of this extrusion process was also carried out to determine the metal flow, temperature evolution and effective strain distribution, which were then correlated with the observed microstructural changes. Although all extruded samples were found to have a bimodal microstructure consisting of equiaxed fine recrystallized (DRXed) grains and elongated coarse unDRXed grains, the inhomogeneity of their microstructural characteristics (i.e., DRX fraction and texture intensity) decreased in cross section with an increase in the Die Angle. The FEM analysis also demonstrated that a faster metal flow, higher temperature, and larger effective strain are generated in an alloy extruded with a 90° Die Angle, and that this enhances DRX behavior during extrusion and ultimately results in a homogeneously DRXed microstructure.
C P Chang - One of the best experts on this subject based on the ideXlab platform.
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effect of Die Angle on the deformation texture of copper processed by equal channel angular extrusion
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001Co-Authors: W H Huang, L Chang, C P ChangAbstract:Abstract The deformation texture of copper processed by equal channel angular extrusion (ECAE) was investigated with two different Die Angles. For specimens deformed by different Die Angles, the preferred orientations were found different, which was attributed to the different orientations of the shear plane with respect to the measuring plane for different Die Angles. It has been demonstrated that the ECAE deformation texture resulted from different Die Angles can be analyzed in terms of the crystallographic orientations of the shear plane and the shear direction in ECAE. The shear direction in ECAE was found essentially parallel to the 〈110〉 direction in copper. This study has confirmed that the ECAE technique does produce a deformation texture similar to that of simple shear (torsion).
David G Morris - One of the best experts on this subject based on the ideXlab platform.
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influence of processing temperature and Die Angle on the grain microstructure produced by severe deformation of an al 7 si alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: I Gutierrezurrutia, Ma Antonia Munozmorris, I Puertas, C Luis, David G MorrisAbstract:Severe plastic deformation by equal-channel angular pressing has been carried out to high strains by repeated pressing using both a high-strain Die and a moderate-strain Die at both room temperature and at intermediate temperature. The Die used appears to play no role in determining the saturation grain and dislocation microstructure after very high strains, with similar submicron grains, high dislocation densities, and silicon particle refinement observed. A slight tendency to microstructural non-uniformity is seen with the high-strain Die. Severe plastic deformation at intermediate temperature leads to a coarser grain size, lower dislocation density, and precipitation of silicon from solution. The extent of grain coarsening, dislocation recovery and precipitate growth is much greater than when annealing room-temperature deformed material, since the high dislocation density accelerates precipitate formation and growth. Material strength is well described by the respective contributions of grain boundaries, dislocations, and precipitates.