Evolution Of Grain Orientation Research Articles

Evolution of crystalline misorientations in polycrystalline samples of pure ice

There are few studies where the evolution of grain orientations and crystal misorientations of neighboring grains in a polycrystalline ice sample during grain growth are analyzed. In this work, crystal orientations and misorientations were studied in two ice cylinders obtained from bidistilled water using the techniques of plastic replicas and chemical etching pits. The cylinders were grown, one through fast freezing and the other through slow freezing. It was observed that the initial crystal orientations of the grains varied from one cylinder to the other, but this did not result in significant differences in the final crystal misorientations between neighboring grains. Such crystal misorientations could be special because they are related to a coincidence sites lattice (CSL), which could be associated with low-energy grain boundaries. Therefore, the decrease in grain boundary energy during grain growth could be influenced by these special crystal misorientations.

Microstructure evolution and EBSD analysis of multi-principal element alloy coatings after high-temperature oxidation

Multi-principal element alloy coatings (MPEACs) have great application potential for high-temperature diffusion barrier coatings. The sluggish diffusion and lattice distortion of this new coating material due to its own atomic size effect give the coating excellent resistance to high temperature oxidation and grain coarsening. In this study, the high-temperature oxidation properties, and microstructure evolution of quaternary, quinary, senary, and denary alloy coatings (whose lattice distortion magnitude is linearly increased) at 1100 °C were studied. The evolution of grain orientation, size, and grain boundaries of alloy coatings after high temperature exposure were analyzed by EBSD. The results showed that from quaternary to denary alloy coatings, with the rise in lattice distortion magnitude of the alloy system, the sluggish diffusion ability of the coating at high temperatures was more obvious. Specifically, the oxidative activation energy of quaternary to denary alloy coatings is 355.41, 480.96, 478.76, and 654.03 kJ/mol, respectively. A high distortion magnitude is beneficial to increase the activation energy of the alloy coating, as a result, grain growth of alloy coatings with high activation energy is significantly inhibited, and under the combined action of storage strain energy and solute dragging, the grain boundary migration rate of the coatings also declines. Finally, the denary alloy coating shows good resistance to high temperature softening. This study provides a positive reference for promoting the application of multi-principal alloys in diffusion barrier coatings.

Effect of Q value on geometric tolerance, roughness and texture evolution of GH4145 alloy tubes

The Q value represents the ratio of the relative reduction in the wall thickness to the relative reduction in the outer diameter during cold-rolling of a tube. The influence of the Q value on the geometric tolerance, roughness, and plastic deformation was determined through laser scanning confocal microscopy, white light interferometry, and electron backscattering diffraction. In this study, nine tube blanks with the same specifications were divided equally into three groups. The outer diameter of each group was reduced by 1 mm, 2 mm, and 3 mm, and the wall thickness of each tube blank was reduced by different amounts. Thus, each group contained one tube with Q values of 0.76, 1.52, and 2.28. Compared with the corresponding blank, the eccentricity, ovality, and roughness of the tube were reduced with a Q value of 0.76. The ovality and roughness of the tube were decreased and the eccentricity was increased with a Q value of 2.28. The eccentricity, ovality, and roughness of the tube were increased with a Q value of 1.52. In terms of texture evolution, with an increase in Q, the < 101 > //radial-direction (RD), < 111 > //axial-direction (AD), and < 101 > //tangential-direction (TD) fibre textures first increased and then decreased. The texture strength was the highest in tubes with a Q value of 1.52, mainly concentrated in the Goss, {011}< 122 > , and copper texture. In the cold-rolling process, the plastic deformation of the tube with a Q value of 0.76 was uniform throughout the section; the plastic deformation of the tube with a Q value of 1.52 near the inner wall was greater; the plastic deformation of the tube with a Q value of 2.28 near the outer wall was even greater. In summary, in the cold-rolling process, the Q value affects the location of plastic deformation and the evolution of grain orientation, which affects the flow of materials and ultimately affects the geometric tolerance and roughness of the tube. Thus, a tube with good surface quality and high-dimensional precision can be obtained by controlling the Q value.

Strain-induced grain boundary migration and grain rotation in polycrystalline metals: Atomic-and meso-scale phase field simulations

The study reveals that in phase field (PF) simulations with over 300 grains, grain boundary (GB) migration exhibits anisotropic behavior and higher velocities under applied external loading. However, these simulations fail to provide detailed atomic-scale information about the evolution of grain orientation. Therefore, the researchers utilize phase field crystal (PFC) simulations to track the evolution of dislocation configurations and the annihilation of GB dislocations. The PFC simulations confirm a newly proposed plasticity process in nanocrystalline metals, where grain rotation is primarily dominated by dislocation climb and dislocation absorption at triple-junction points on GB, rather than GB sliding or diffusional creep as previously suggested. Furthermore, the PFC simulations demonstrate that the analysis of misorientation angles and GB dislocation evolution between neighboring grains can be quantitatively described using the Frank-Bilby equation. Thus, a hybrid approach of PF and PFC successfully describes in-situ transmission electron microscopy observations of GB migration and grain rotation for the first time. This multi-scale simulation method provides a deeper understanding of plasticity formation and development in nanostructured materials.

Study on quasi-in-situ tensile microstructure evolution law of 5052-O aluminum alloy based on EBSD

SHIMADZU AGS-100KN universal testing machine was used to carry out tensile experiments of 2.2%, 5%, 10%, 15%, 20% and 25% of different tensile elongations on 5052-O aluminum alloy. The surface DIC morphology characteristics and the evolution law of the microstructure of samples under different elongation rates were studied by the DIC (digital image correlation) and the EBSD (electron backscatter diffraction). The results show that the tensile strength of the 5052-O aluminum alloy reaches the maximum value of 205.632 MPa and the elongation at failure is 28.8%. When the tensile deformation is 2.2%, there is an obvious slip band at 45° to the direction of the tensile axis. At 10% deformation, the slip band is obviously narrowed, with darker interior color and large deformation. With the gradual increase of the deformation, the proportion of the microstructure recrystallization area and the substructure area decreases, and the proportion of the deformation area increases. The plastic deformation mechanism is mainly the dislocation slip. The low angle grain boundary gradually increases and the high angle grain boundary decreases as the increase of deformation. When the deformation is above 15%, the changing trend of low-angle and high-angle grain boundaries also slows down. During the tensile deformation process, the corresponding KAM (Kernel Average Misorientation) value distribution curve value is constantly moving to the right and expanding. The R-type texture {124}< 211 > always exists, the Brass texture {110}< 112 > and the S-type texture {123}< 634 > keep increasing. • During the quasi-in-situ tensile test of the 5052-O aluminum alloy sample, the change of the sample morphology was continuously recorded by DIC. It can dynamically observe the microstructure changes of the specimen during the tensile process. • EBSD was used to study the evolution of grain orientation, the change of recrystallization region and the statistics of crystallographic orientation difference of specimens under different deformations during tensile deformation. It reveals the stress concentration mechanism in the deformation region and discusses the evolution of texture after tensile deformation. It provides some theoretical basis for the process optimization in industrial production. • Through the analysis of the texture evolution, the R-type texture {124}< 211 > existed during the deformation process. The Brass texture {110}< 112 > and S-type texture {123}< 634 > continued to increase with the tensile deformation increased.

Evolution of Grain Orientation in front of the Pin during FSW of the 6082-T6 Aluminium Alloy

Friction stir welding (FSW), a new solid-phase connection method, is considered an excellent welding method for aluminium alloys. Grain orientation, grain boundary structure, and texture types in different regions were characterized by a high-resolution electron backscattered diffraction technology. The results revealed that during the welding process, the coarse grains of the base metal are refined, grains in region 1 (600 μm away from the edge of the keyhole) are arranged in a long strip, and the long axis is approximately parallel to the shear direction. The thermal cycle of the welding process causes some grains to recrystallize, further forming a recrystallization (100) [011] rotating-cube texture. The metal in region 2 (100 μm away from the edge of the keyhole) was severely squeezed by the pin, resulting in an increase in the degree of grain breakage in this region, which were mainly equiaxed grains. Due to the eccentric movement of the pin, the (100) [001]-oriented and (110) [001]-oriented grains alternate on the middle layer, forming a banded structure. Plastic deformation and recrystallization occurred in the base metal, within 383 μm in front of the pin, forming a (110) [001] Goss texture and (100) [001] recrystallized cubic texture.

Non-uniform deformation behavior of dissimilar friction stir welded AM60/AZ31 joint and its influence on fracture

In this work, the defect-free dissimilar AM60/AZ31 Mg joint was obtained by friction stir welding (FSW). Tensile tests were employed under different stress states to investigate the tensile behavior of the joint. The joint microstructures before and after deformation were characterized via electron backscatter diffraction to reveal the relationship between the microstructure and the deformation and fracture behaviors. The results indicated that a significant and complex evolution of grain orientation generated in the joint after FSW. The grain size of the weld bottom was smaller than that of the upper-middle part. However, compared with the base materials, the grains in upper-middle part were not refined obviously for the high welding heat input. In addition, there was a triple junction region (TJR) with significant texture fluctuations in the upper area of the weld. Further, the reasons for the fracture of joint approximately along the centerline of nugget zone (NZ) in the back face and both the NZ and the TJR interfaces in the front face were explained. During the tensile process, cracks initiated at the bottom of NZ-center in the back face due to the appearance of compression twins and double twins. Cracks developed towards the AM60 side owing to its larger grain size. Further, near the NZ boundary was a favorable orientation for basal slip and extension twinning, which was more prone to deformation and thereby made cracks terminate here. Meanwhile, there were significant differences in texture distribution and grain size in the different parts of TJR. This resulted in an incompatible deformation between the micro-regions, making cracks easily develop along the interface of these micro-regions.

Amorphous shear bands in SmCo5

Formation of thin amorphous shear bands has been recently shown to enable plastic flow in crystalline SmCo5 in the absence of dislocations. To bring insights into the criteria for when this mechanism can be active, here we analyze energetics and atomic structure of deformation-induced shear bands in SmCo5. We find that the formation energy of amorphous shear bands is significantly lower than cleavage energies on different crystallographic planes. The density of the atoms in the shear bands decreases by less than 2% due to the amorphization, which indicates a very small dilation. Analysis of local ordering shows that the amorphous shear bands are more disordered than a melt-quenched sample and the overall fraction of icosahedra is much lower than usually reported in metallic glasses, such as Cu–Zr. The influence of amorphous shear bands on the evolution of grain orientations is also discussed.

Influence of Guillotine Clearance on Cut-Edge Damage to Nonoriented Electrical Steel

Nonoriented electrical steel of 0.65 mm thickness was sheared to investigate the influence of guillotine clearance on cut-edge damage. The result shows that all the burr, work hardening, and magnetic property damage present an increasing trend initially, then a decrease, followed by an increase with increasing guillotine clearance. In particular, when the relative guillotine clearance (c/t) is within 4.6-6.2%, the burr is small and the cut edge is only slightly damaged. Damage to the burr, work hardening, and magnetic properties are influenced and inter-correlated. The plastic deformation of the microstructure at different c/t ratios is the decisive factor affecting burr forms and cut-edge damage. On the one hand, it leads to different degrees of work hardening and then results in a diversity of crack propagation patterns, forming burr and cross-sectional morphologies with different shapes. On the other hand, the stress distribution and grain orientation also change, which further influences the magnetic properties. Moreover, the relationship between microstructure deformation and grain orientation was established by analyzing texture occupancy and orientation distribution function diagrams. It is clarified that both nucleation position evolution and edge stresses generated by different clearances contribute to the evolution of grain orientation and texture.

Secondary Recrystallization Goss Texture Development in a Binary Fe81Ga19 Sheet Induced by Inherent Grain Boundary Mobility

Secondary recrystallization Goss texture was efficiently achieved in rolled, binary Fe81Ga19 alloy sheets without the traditional dependence on inhibitors and the surface energy effect. The development of abnormal grain growth (AGG) of Goss grains was analyzed by quasi-situ electron backscatter diffraction (EBSD). The special primary recrystallization texture with strong {112}–{111}&lt;110&gt; and weak Goss texture provides the inherent pinning effect for normal grain growth by a large number of low angle grain boundaries (&lt;15°) and very high angle grain boundaries (&gt;45°) according to the calculation of misorientation angle distribution. The evolution of grain orientation and grain boundary characteristic indicates that the higher fraction of high energy grain boundaries (20–45°) around primary Goss grains supplies a relative advantage in grain boundary mobility from 950 °C to 1000 °C. The secondary recrystallization in binary Fe81Ga19 alloy is realized in terms of the controllable grain boundary mobility difference between Goss and matrix grains, coupled with the orientation and misorientation angle distribution of adjacent matrix grains.

Evolution of grain orientation and texture of copper and steel in copper cladding steel wires during drawing and annealing

The microstructure, grain orientation and texture of copper and steel in copper cladding steel (CCS) wires during drawing and annealing were investigated by using EBSD. The results showed that the copper grains and ferrite grains of steel in CCS wires are elongated along the drawing direction and transformed to fiber microstructure. The microstructure of copper and steel in CCS wires experiences recovery, recrystallization and grain growth after annealing treatment. The elongated copper grains and ferrite grains of steel gradually transformed to equiaxed grains and the grain sizes increased with annealing temperature increasing. With the increase of deformation amounts, the misorientation angle of copper and steel changes from large angle to small angle and the texture variation of copper is not obvious, which is inconsistent with the texture change of pure copper wire. However, the texture variation of steel is consistent with that of a single steel wire, mainly the fiber texture in the direction of <110>. With the annealing temperatures increase, the misorientation angle of copper and steel changes from small angle to large angle. The variation of texture with annealing temperature is similar to that of single copper and steel wires. For copper, when annealing temperature is less than 850 °C, the intensity fluctuation of texture is not very obvious. The <111>-<211> texture becomes diffused. However, when annealing temperature is more than 850 °C, the texture included a number of strong <111> annealing texture and a few of weak <110> annealing texture. For steel core, the <110> fiber texture doesn’t disappear and only the fiber texture transforms to the annealing texture. The intensity of texture increases slightly with increase of annealing temperature.

Quantitative analysis of orientation and near neighbor interaction effects during deformation of polycrystalline Ti6Al4V

The effect of orientation and interaction with neighboring grains in polycrystalline Ti6Al4V deformation are quantified using interrupted deformation coupled with microstructure analysis. It is shown that softer grains accommodate more strain compared to hard basal grains, which can be explained in terms of their resolved shear stress and critical resolved shear stress. Grains with similar orientations follow different orientation trajectories during deformation depending on their misorientation with respect to neighboring grains. The influence of near neighbor interaction is quantified using a new parameter, average nearest neighbor misorientation (NNM). The NNM accurately predicts similarities and differences in the evolution of grain orientations during deformation.

Micro-deep Drawing on Aluminium Crystals in Order to Validate Multiscale Modeling

This paper introduces the application of micro-deep drawing of single and multicrystals of aluminium in order to identify parameters of micro-mechanical models. The information obtained experimentally is abundant: load-displacement curves of the punch, the evolution of grain orientation, mapping deformations throughout the test. All this experimental data was used to validate the multiscale models introduced in a finite element code for loading paths ranging from biaxial tensile to simple tensile.

Effect of Cryogenic Treatment on the Microstructure and Mechanical Properties of AZ31 Magnesium Alloy

The effect of cryogenic treatment (77 K) on the microstructure and mechanical properties of magnesium and AZ31 magnesium alloy has been investigated in this article. The results show that tensile stress and the hardness of the samples treated in a cryogenic environment are higher than those of the untreated samples. The improvement of mechanical properties is highly dependent on the soaking time. The main reason for the improvement of mechanical properties could be ascribed to the generation of a type of “frame-like” twinning during the cryogenic treatment, which also leads to the evolution of grain orientation.

Texture memory effect in heavily cold-rolled Ni 3Al single crystals

In Ni 3Al the cold-rolled Goss texture changed to a complicated one after primary recrystallization and returned to the original Goss during the subsequent grain growth, which can be referred to as the texture memory effect. In this study, we examined the evolution of grain orientations during the grain growth using the electron backscatter diffraction (EBSD) method. It was found that just after the primary recrystallization most of the grains had a 40°〈1 1 1〉 rotation relationship to the Goss texture, the remaining grains being Goss and other textures. The formation of the 40°〈1 1 1〉 rotated grains can be explained by a multiple twinning mechanism. In the grain growth, the Goss grains, which were surrounded by the 40°〈1 1 1〉 rotated grains, grew preferentially due to the high mobility of the 40°〈1 1 1〉 grain boundaries, leading to the texture memory effect.

Grain Growth in Thin Films

in the average crystal orientation and can even result in epitaxial films. It is therefore not surprising that grain growth can profoundly affect the mechanical, electrical, and chemical properties of thin films. In this article the mechanisms and modes of grain growth in thin films will be reviewed. The focus will be on those factors that lead to the evolution of grain orientations as well as grain si zes. Spec ific attention will also be gi ven to those factors that allow control of microstructural evolution in thin films.