Papers by Keyword: Texture

Abstract: Severe plastic deformation (SPD) with strong shear component is required to promote both grain refinement and texture randomization. When Asymmetric rolling (AR) is applied as asymmetric accumulative roll bonding (AARB), it enables the production of architectured microstructures and metallic composites. Finite element (FE) simulations of AR and AARB were employed to understand the influence of pass thickness reduction (PTR) on the through thickness variation of the velocity gradient. The influence of the PTR up to a total thickness reduction of 50% and the effect of a single 50% reduction step in a bi-layer bonding condition was analyzed. The influence of these process parameters on the strain and rigid body rotation components was compared with the experimental data obtained on an AA1050 aluminum. A better shear to compression ratio across the sheet thickness is achieved by PTRs lower than 30%; at a PTR of 50% the texture is dominated by the frictional shear generated at the roll-sheet interface and the process has a stronger compressive character. This indicates that simple ARB followed by AR with smaller PTRs should generate a better shear distribution than AARB alone.

Abstract: Microstructure and crystallographic texture play an important role in the sputtering target properties. The effect of asymmetric cross rolling (ACR) and deformation strain during ACR on texture homogeneity is not clear. Thus, high-purity tantalum (Ta) plates were ACR to 60% and 87% reduction in thickness. Texture of the rolled Ta sheets in the surface and center layer are characterized via X-ray diffraction (XRD). The XRD results indicate that ACR is effective to weaken the texture gradient existing in the as-received Ta plate. Besides, more homogeneous texture distribution along the thickness can be obtained with the increasing strain during ACR process.

Abstract: Studies regarding the recrystallization texture of brass alloys are quite complex. Previous experiments showed that the addition of the alloying elements on brass alloys affect the deformation mechanism and texture development. Alloying elements promoted the inhomogeneous deformation and resulted in a heterogeneous microstructure. During annealing, the new grains form around the shear band area and develop the random texture. This research studied the effect of Mn addition on the recrystallization characteristics and texture development of Cu-29Zn alloys. The Cu-Zn-xMn alloys were produced by gravity casting with a dimension of 110x110x6 mm³. The feeding material includes pure Cu, Zn, and Mn. The as-homogenized samples were then cold-rolled with the level of deformation of 70 % and followed by an annealing process at temperatures of 400, 500, and 600°C. Samples characterization includes chemical composition analysis, microstructure observation, hardness testing, and texture measurement. The results showed that the addition of Mn tended to reduce the rate of recrystallization and grain growth. At 70% deformation, Mn addition promoted the formation of brass and Goss texture. The presence of Mn also influenced the formation of recrystallization and annealing texture.

Abstract: In this paper, the evolution of texture in the ferrite phase and mechanical behavior of cold-drawn pearlitic steel wires produced for strand manufacturing at Trefisoud company was investigated. Wire drawing induces the development of dislocation density, reduction of interlamellar spacing and the refinement of grains size which leads to a strong hardening of the wires. That explains the increase of the tensile strength from 1242 MPa to 2618 MPa with higher deformation. Also, the cementite lamellae are rotated toward the drawing axis and the thickness of lamellae further decreases when strain level increases, this phenomenon leads to a somewhat fibrous structure. The quantitative analysis obtained by EBSD data shows the development of a strong (<110> // ND) texture of the ferrite phase leading to a structural transformation from isotropic to anisotropic.

Abstract: AZ80+0.4%Ce alloy ultra-thin-walled tube with a wall thickness of 0.6 mm was fabricated by multi-pass variable wall thickness extrusion (VWTE) at 693 K. Microsturcture and texture evolution were investigated. The results indicate that the average grain size decreases from ~47 μm of extruded alloy to ~8.9 μm after 5 passes VWTE. The total area reduction of Mg alloy tube is 91 %. Homogeneity of microstructure is improved obviously and the morphology of Mg₁₇Al₁₂ phases in coarse grains and fine DRXed grains exhibit lamellar and granular shapes, respectively. In addition to the microstructure evolution, the VWTEed tubes showed a strong texture of (0001) planes, and the intensity decreased with deformation increasing to 4 passes. After 5p-VWTE, a strong texture characterized by (0001) pole tilting 20 degrees rotated from extrusion direction (ED) towards normal direction (ND).

Abstract: Severe plastic deformation can be produced by repetitive upsetting-extrusion process. Using the repetitive upsetting-extrusion (RUE) process at decreasing temperature, the Mg-12.0Gd-4.5Y-2.0Zn-0.4Zr (wt %) alloy was deformed by different RUE passes and then heat treated. The microstructure, texture and mechanical properties of the alloy were compared and analyzed. The results demonstrate that with the increase of deformation passes, the coarse grains of the alloy decreased, the dynamic recrystallization fraction increased, and the dynamic recrystallized grains phagocytized the original grains. This can promote the continuous refinement of the grains and the microstructure uniformity. The maximum texture intensity of the (0001) basal plane decreased significantly with the increase of processing passes and the dispersion degree of pole figure increased. The orientation of dynamic recrystallized grains was randomly distributed to weaken texture. Due to the refinement of microstructure and the weakening of texture, the tensile strength and yield strength of the alloy obviously increased at room temperature. The mechanical properties of the alloy reached the highest after 3 passes and heat treatment.

Abstract: The tensile deformation process and dislocation behavior of primary α-Ti of Ti-6Al-4V were studied by the in-situ tensile test combined with EBSD (electron backscatter diffraction). The initiation, evolution and distribution of dislocation slips at different strains were discussed. The results showed that the microtexture of the material had a significant influence on slip behavior. Typically, basal and prismatic <a> slips initiated first, but the dominant slip type was related to the local texture characteristics. Sometimes, the basal and prismatic <a> slips could still initiate when their Schmid factors were relatively low, while the pyramidal slips usually need a higher Schmid factor to initiate. With the increase of strain, the second slip system inside one grain was activated to accommodate the plastic deformation. When the deformation was localized in a specific microtextured region, basal <a> slips were dominant, but eventually the crack initiated from the <c+a> slip bands inside the grain.

Abstract: The effect of ferritic hot rolling process on microstructure and properties of Ti microalloyed IF steel was investigated. The hot rolling-coiling, cold rolling and continuous annealing processes of ferritic zone were physically simulated. The influence of thermal deformation (finishing rolling temperature, coiling temperature) on the structure, texture and forming properties of Ti-If steel was studied through tensile test, EBSD, XRD and other analytical methods. The results showed that the recrystallization occurred after hot rolling and coiling in the ferritic region. Weak α-fiber and weak γ-fiber were obtained in the central layer of hot rolling plates, and the strength of γ-fiber was higher when finished rolling at low temperature. α-fiber and weak γ-fiber were strengthened after cold rolling. After annealing, the α-fiber was weakened and the γ-fiber was strengthened, and the γ-fiber became the main texture. The larger and more uniform grain size and better mechanical properties were obtained by IF steel finished rolling and coiling at high temperature and after continuous annealing, reaching yield strength of 106 MPa, tensile strength of 297 MPa, elongation rate of 52%, n value of 0.26 and r value of 2.3. The hot rolling texture is hereditary. If the more γ-fiber is formed after hot rolling, the more γ-fiber recrystallization texture is formed after cold rolling and annealing.

Abstract: Mechanical properties and texture of tube material formed in the process of tube production were studied. Texture in tubes was estimated by contractile strain ratio (CSR) according to requirements of the standard for tubes. Mechanical properties depend on CSR. Optimal values of mechanical properties were determined: ultimate strength, yield strength and relative elongation which provide CSR values within 1.3...3.5. The texture was evaluated in the process of tube manufacture. An increase in radial component of the texture leads to an increase in CSR. At high CSR values up to 3-3.5, tubes often do not withstand process tests for flattening and bending. Correction of CSR values is required. It was shown that an increase in ductility of tubes increases the value of CSR.

Abstract: The study considers the formation of the structure, texture, and hardness of hot extruded tube of titanium alloy PT-1M. It is shown that hot extrusion at 840 °C, which is higher than the α-phase recrystallization temperature, results to the development of dynamic and primary recrystallization processes and ensures the formation of homogeneous and fine-grained structure through-out the cross section with a two-component tangential texture (0001)TD<100>ED+(0001)TD<110>ED (TD – tangential direction, ED – extrusion direction) and hardness of 155 HV. It has been established that a higher cooling rate of the surface areas of the tube after extrusion results to a less active development of recrystallization processes, which lead to the formation of a finer granular structure near the outer surface. This weakens recrystallization component of (0001)TD<110>ED, compared to other areas of the tube.