Growth Of Cube Grains Research Articles

The influence of deformation texture on nucleation and growth of cube grains in aluminium

The influence of deformation texture on the initial stages of recrystallization of deformed pure Al single crystals and commercial AA1050 alloy were characterized. To precisely quantify the orientation relationship between nuclei and simple deformation structures, single crystalline samples of stable Br(110) [1-1-2] and semi-stable S’(234) [20-28 11] orientations, were plane strain compressed (PSC) to 40% to develop a dominant homogeneous microstructure composed of two sets of microbands. The samples were then lightly annealed to reach the initial stage of primary recrystallization. The results on single crystals were related to the behaviour of the polycrystalline samples in state after hot-rolling then PSC to the same degree and lightly annealed. SEM/EBSD analyses of single crystalline samples demonstrate that the orientations of recrystallized grains are limited to a certain number of orientation groups. However, the orientations of the as-deformed state are not retained in the orientations of new grains. Deformed samples with Br orientation do not show the formation of cube grains during recrystallization, whereas strong nucleation of cube-oriented grains is observed in homogeneously and heterogeneously deformed areas in the semi-stable S’ orientation, despite the cube-oriented nuclei not present in the as-deformed structure. The recrystallization texture components of the AA1050 alloy were related to the standard β-fibre texture formed during the previous cold deformation. Cube grains formed intensively in PSC polycrystalline samples, primarily in association with as-deformed areas with near four variants of S(124) [21-1] and S’ orientations and were characterized by local misorientations around the <111> axes.

The influence of deformation texture on nucleation and growth of cube grains during primary recrystallization of AA1050 alloy

The influences of microstructure and texture on the early stages of recrystallization of a commercial AA1050 alloy have been characterized with particular attention to cube grain formation. Samples were deformed along two deformation modes to form different as-deformed texture components and then lightly annealed: one group was plane strain compressed (PSC) in a channel-die, whereas the second group was deformed by equal channel angular extrusion (ECAE). The textures were measured by X-ray diffraction and SEM/EBSD. After both deformation modes a very weak residual cube texture component was observed in the samples. Cube-oriented grains were not formed during annealing of the ECAE samples whose main as-deformed texture components were close to {124}<651>. During recrystallization these transformed to two components of ∼{100}<011> and ∼{221}<114>-type essentially by <110> rotations. Cube grains were extensively formed only during annealing of PSC samples. They were situated preferentially inside or in between the S-oriented deformed areas with local misorientations about <111> axes.

Structural Refinement, Recrystallization and Grain Growth Phenomena in an Accumulative Roll Bonded Nickel Sheet

The thickness of the lamellar band (LB) structure that is generated in an accumulative roll bonded nickel sheet represents the degree of structure refinement. The LBs reach a saturation in thickness after several roll bonding cycles due to adiabatic heating that balances the dislocations generated during rolling. The thermal restoration process starts with the rearrangement of dislocations and boundary migration. At the initial stages of thermal restoration, LBs with all the orientations in the deformation texture grow by the so-called continuous recrystallization process. However, in the latter stages, growth becomes orientation selective and dominated by S and copper orientations. Finally, grain growth after recrystallization results in the preferred growth of Cube-oriented grains to the full layer thickness of the ARB sheet, thereby generating a strong Cube texture. Thus, grain growth yields a final texture similar to that generated in conventionally rolled and annealed nickel sheets.

In-situ annealing and computation study of cube texture development in a commercial aluminum alloy

AbstractThe aim of this study was to identify the physical processes of nucleation and growth of cube grains by means of in-situ annealing experiments. The calculated nucleation site density at cube bands was found not to be sufficient for a correct computational prediction of the cube recrystallization texture. Growth competition at an early stage of recrystallization has to be taken into account for a better agreement between model and experiment, which necessitates a sufficiently refined grid resolution in discrete computer models of recrystallization. Accounting for these dependencies yields an excellent prediction of both the cube component in the recrystallization texture and the grain size distribution. The contribution of cube nucleation apart from cube bands to the cube recrystallization texture was found to be negligible.

Evaluation of Texture and Grain Size of Nanograined Copper Produced by the Accumulative Roll Bonding Process

Pure copper was intensely deformed by accumulative roll bonding (ARB) for up to eight cycles at ambient temperature. X-ray diffraction (XRD) was used to evaluate the grain size and texture during the ARB process. The Williamson–Hall method was used to calculate the grain size from the XRD patterns, which was about 30 nm after eight cycles of the ARB process. Texture analysis revealed cube texture in the initial copper. The intensity of cube texture decreased after one cycle of the ARB process. The texture of two-cycle ARB-processed sample was a transition texture, from cube to shear texture (rotated cube) that appeared after two cycles of ARB process in the subsurface regions. This shear texture developed due to shear deformation induced by the high level of friction between the rolls and the sheet. Moreover, shear texture was replaced by recrystallization texture (cube component) by annealing the ARB-processed samples. This result was caused by preferential growth of cube grains.

Analysis of the growth of individual grains during recrystallization in pure nickel

The growth of individual grains during recrystallization in 96% cold-rolled pure nickel has been followed using electron backscatter pattern maps of the same surface area taken after each of several annealing steps. It was found that the growth is quite complex, with boundaries moving, stopping and moving again. The growth kinetics differ from grain to grain and, on average, cube-oriented grains grow the fastest. The growth of the grains has also been analyzed as a function of boundary misorientation. This analysis shows that there is no significant difference in misorientation distribution between boundaries that move and those that do not. This is contrary to the usual assumption that the boundary mobility and the migration rate depend on the misorientation across a boundary. This observation and the reasons for the faster growth of cube-oriented grains are discussed.

In Situ EBSP Analysis of Grain Boundary Migration during Recrystallization in Pure Aluminum Foils

Grain boundary mobility in preferential growth of cube grains ({100}&lt;001&gt;) was evaluated by in-situ electron back scattering diffraction pattern (EBSP) analysis in order to clarify the fundamental mechanism of primary recrystallization in pure aluminum foils of 99.9% purity thermo-mechanically processed in the industrial production route for aluminum foils for electrolytic capacitors. We have carried out the continuous EBSP measurements during recrystallization of the aluminum foils heated to various temperatures in the chamber of scanning electron microscopy (SEM). We have succeeded in dynamic observation of the preferential growth of cube grains by the in-situ EBSP analysis. The in-situ EBSP analysis could reveal the migration rate of grain boundaries surrounding the cube grains. It was clarified that the proportional relation between migration rate and annealing time was satisfied. The stored energy providing the driving force for the grain boundary migration during primary recrystallization could be estimated from the misorientation within the deformed grains. The mobility of the grain boundary could be evaluated using the measured grain boundary migration rate and stored energy. Then the activation energy could be estimated by the in-situ EBSP analysis at various temperatures ranging from 270°C to 310°C. The obtained activation energy was 124 kJ/mol, which approximately corresponded to that for the diffusion of impurity such as iron or silicon in aluminum. This suggested that the rate-determining process of the grain boundary migration of cube grains was impurity diffusion in the pure aluminum foils.

Annealing Behavior and Recrystallized Texture in ARB Processed Copper

The recrystallization behavior and texture development in copper accumulative roll-bonding (ARB) processed by various cycles (2, 4 and 6 cycle) were studied by differential scanning calorimetry (DSC) analysis and SEM/EBSP method. The exothermic peaks caused by recrystallization appeared at 210 ~ 253 􀍠 in each sample. The peak positions shifted to lower temperature as the number of ARB cycles increased. This result indicated that the evolution of finer microstructure with increasing number of the ARB cycles enhanced the occurrence of recrystallization at lower temperature. The stored energy calculated from the DSC curve of the ARB processed copper increased with the increasing strains. During an annealing, the preferential growth of cube-oriented grains ({100}&lt;001&gt;) occurred in each sample. The recystallization behavior of ARB processed copper having low stacking fault energies was distinguished from that of so-called “recovery type” materials, i.e. aluminum and low carbon steels, which shows rather continuous changes in microstructure during annealing. The accumulated strains provided the driving force for the preferential growth, which was the same mechanism as the preferential growth in normally rolled copper. The sharpest cube texture developed in ARB processed copper by 4 cycles. The difference of cube texture development between 2 cycles and 4 cycles was caused by the distribution of cube-oriented regions which corresponded to the nucleation sites of recrystallized grains before annealing. More nanocystalline layers in the vicinity of bonded interfaces were distributed in ARB processed copper by 6 cycles than 4cycles. The nanocystalline structure could grow faster than the cube-oriented grains and led to the inhibition of sharp cube texture in the ARB processed copper by 6 cycles.

Abnormal Grain Growth of Off-Cube Grains in High Purity Aluminum Foils with Cube Texture

In present study, abnormally coarsened grains in high purity aluminum foils with cube texture (f100gh001i) after a final annealing was investigated using SEM/EBSP method. Most of abnormally coarsened grains had Goss (f110gh001i )o r S( f123gh634i) orientations. The coarsened grains with Goss and S-orientations were surrounded by �5 and �7 coincidence boundaries, respectively. This result clarified that these coincidence boundaries would enhance the abnormal grain growth of Goss and S oriented grains. Grain boundary energy of sub-boundaries between cube-oriented grains provided the driving force for the abnormal grain growth. The distribution of Goss oriented grains in the partially annealed foils was characterized by SEM/EBSP method. This characterization revealed that many Goss-oriented grains were distributed in the transition band on the central layer of the sheets. aluminum and its alloys, which is closely related to forming or etching property. Several thermo-mechanical processes have been developed for the control of cube texture in commercially pure aluminum and its alloys. A thermo- mechanical process through a cold rolling, a partial annealing (the annealing temperature is 240-260 � C), an additional rolling (the reduction in thickness is approximately 20%) and a final annealing has been developed for the formation of sharp cube texture in a high purity aluminum and an Al-Mn- Mg alloy, 2) which are referred to as Pechiney process. 3) This process is the production process for aluminum foils for electrolytic capacitors. The mechanism of preferential growth of cube-oriented grains (cube grains) by the Pechiney process has been investigated using SEM/EBSP method. 4,5) The previous investigations have clarified that the difference of accumu- lated strains between cube grains and off-cube grains induced by an additional rolling could provide the driving force for the preferential growth of cube grains during the final annealing. This mechanism is expected to have come from the property that cube grains have less accumulated strains than off-cube grains. 6) Hence Controlling the formation of substructure accelerated the preferential growth of cube grains and inhibited growth of off-cube grains, leading to the production of higher volume fraction of cube texture more than 95%. 7) However, in some cases, off-cube grains abnormally grow to over 10 cm in grain size in high purity aluminum sheets through the Pechiney process, and bring about decline of a volume fraction of cube texture. Most of recent studies 8-14) are concerned to the preferential growth of cube grains, so that there are few studies on the character of residual off-cube grains in aluminum sheets with cube texture. Accordingly, establishing the mechanism of the formation and growth of off-cube grains in aluminum sheets with cube texture is important for not only the development of processes for control of cube texture but also under- standing the fundamental mechanism of cube texture devel- opment in aluminum and its alloy. In the present study, off-cube grains in high purity aluminum foils with cube texture were analyzed by SEM/ EBSP method. From the results, the mechanism of abnormal growth of off-cube grains is discussed focusing an attention to mobility and driving force of grain boundary migration between cube grains and off-cube grains. A distribution of orientation in aluminum foils before the final annealing was characterized by SEM/EBSP method. Comparing the dis- tribution of off-cube grains in the foils before and after the final annealing, we discuss the mechanism of the formation of off-cube grains during the thermo-mechanical process. 2. Experimental

Influence of Purity on the Formation of Cube Texture in Aluminum Foils for Electrolytic Capacitors

In the present study, the crystal orientation and residual strains in hot rolled sheets, cold rolled foils, partially annealed foils, and additionally rolled foils of aluminum of 99.9% (3NAl) and 99.99% (4NAl) purity used for the fabrication of electrolytic capacitors, were evaluated by the SEM/EBSP method. The additionally rolled foils were annealed at 573 K and the behavior of the growth of cube-oriented grains and the grain boundary character were analyzed. In the hot rolled sheets and the partially annealed foils, cube-oriented grains in 4NAl were larger in number and size than those of 3NAl. From the result, it was clarified that purity of the aluminum affected the growth of cubeoriented grains during the thermo-mechanical treatment. In the additionally rolled foils annealed at 573 K, the growth of the cube-oriented grains in 4NAl was faster than that in 3NAl. In both 3NAl and 4NAl, the residual strains and the grain boundary character were similar. Accordingly, it is concluded that impurity in 3NAl could have segregated at the grain boundaries around cube-oriented grains and supressed the growth of cube-oriented grains.

Preferential Growth of Cube-Oriented Grains in Partially Annealed and Additionally Rolled Aluminum Foils for Capacitors

It is well known that a sharp Cube texture is developed for the producing process of a pure aluminum foil for capacitors. The orientation analysis using scanning electron microscopy/electron backscattered diffraction pattern (SEM/EBSP) method has been performed on the transverse direction (TD) sections of partially annealed (PAed) and additionally rolled (ARed) foils through the thickness in order to reveal how Cube-oriented grains have advantages for growth in comparison with the other grains with orientation components of rolling texture. Samples were annealed repeatedly with increasing the temperature in a vacuum. The Cube grains were distributed throughout foil thickness homogeneously in the PAed and ARed foils. The main mechanism of preferential growth of the Cube grains in the PAed foils was driven by grain boundary energy. However, the growth for ARed foils was caused by strain induced grain boundary migration (SIBM) driven by the difference in stored energy between the Cube and the other grains, because the former store less strain energy than the latter after the additional rolling. Furthermore, the grown-up Cube grains having similar orientations met each other and made a cluster in both the foils. Since the clusters develop to reach the foil surfaces and become stable, the Cube grains are easy to cover all of the foil in the final stage of annealing.

電解コソデンサ用アルミニウム箔の立方体集合組織形成に及ぼす加工熱処理条件の影響

The present study was carried out to clarify the effect of condition of thermo-mechanical treatment (partial annealing and additional rolling) on behavior of cube texture in high purity aluminum foils for electrolytic capacitor. Foils were partially annealed at 503, 523 and 543 K and additionally rolled to 12, 17 and 22% reduction. They were finally annealed at 573 K. All foils were evaluated by SEM-EBSP method. It was elucidated that the foil partially annealed at 523 K and additionally rolled to 17% reduction, had larger area fraction of cube-oriented grains than the other foils after final annealing. From the examination of that, it was concluded that the distribution and diameter of cube-oriented grains depended on the partial annealing temperature and that grain growth in final annealing was affected by the residual strain in grains attributed to the degree of reduction of the additional rolling. It was considered that the optimized condition of thermo-mechanical treatment enhanced growth of cube-oriented grains and suppressed the other grains. On the basis of the theory to bulge nucleation the critical diameter of growth of cube-oriented grains was estimated. The estimated diameter was compared with the distribution of the measured diameter of cube-oriented grain. The result explained well the dependence of the area fraction of cube-oriented grains on foils with different conditions of thermo-mechanical treatment after final annealing.

On the origin of recrystallization textures

The development of recrystallization textures has been debated for the past 50 years. Essentially the rival theories of evolution of recrystallization textures i.e. oriented nucleation (ON) and oriented growth (OG) has been under dispute. In the ON model, it has been argued that a higher frequency of the special orientation (grains) than random occur, thus accounting for the texture. In the OG model, it has been argued that the specially oriented grains have a high mobility boundary and thus can migrate faster and grow to a larger size as compared to random orientations thus contributing to the final recrystallization texture.In FCC metals and alloys like aluminium, cube orientation [(001) 〈100〉] is the recrystallization texture component. In the classic OG model, cube orientation is supposed to be misoriented fromS-orientation [(123)\(\left\langle {62\bar 4} \right\rangle \)] which is a deformation texture component by a 40° about 〈111〉 relationship which is supposed to be a high mobility boundary leading to faster growth of cube grains. Stereographic calculations and analytical calculations are presented in this paper to the effect that theS-orientation (123)\(\left\langle {63\bar 4} \right\rangle \)is not misoriented from cube (100) 〈001〉 by 40° 〈111〉 whereas another deformation texture component (123)\(\left\langle {41\bar 2} \right\rangle \)which is termed theR-component is misoriented from cube component by 40° 〈111〉,R-component is also seen in deformation textures of aluminium and hence the classic OG model remains valid with respect to theR-component.

Growth of cube grains during recrystaIIization of aluminium

Recrystallization in a commercial purity aluminium alloy has been investigated. The development of recrystallization texture and the rate of grain growth during the transformation has been followed by selected area channelling patterns in a STEM microscope. It is documented that the volume fraction of the cube texture component increases at a higher rate than the other texture components during the recrystallization reaction. This behaviour is interpreted as a preferential cube site localization effect.MST/218

Growth of cube grains during recrystaIIization of aluminium

Recrystallization in a commercial purity aluminium alloy has been investigated. The development of recrystallization texture and the rate of grain growth during the transformation has been followed by selected area channelling patterns in a STEM microscope. It is documented that the volume fraction of the cube texture component increases at a higher rate than the other texture components during the recrystallization reaction. This behaviour is interpreted as a preferential cube site localization effect.MST/218

純アルミニウムにおける立方体方位粒のひずみ粒界移動

Preferential growth of cube-oriented grains through grain boundary migration was investigated by microfocused X-ray diffraction. In aluminum 99.99% purity, cube textures with small orientational spread develop when rolled to 90% reduction, partially annealed up to the recrystallization percentages 5 to 40, and additionally rolled to 30% reduction. Cube grains surrounded by deformed matrix are deformed by additional rolling. Cube grains which cause sharp Laue spots at the same position to the asterisms due to the strained cube grains grow into deformed matrix before non-cube grains recrystallize from the deformed matrix upon annealing. Strained cube grains recover without reorientation, and consequently coalesce with strain-free cube grains. Migration of boundary of cube grains and recovery of the strained cube grains take place as easily as the orientations of cube grains are closer to the ideal orientation (001) [100].

THE FORMATION OF CUBE TEXTURE IN AN IRON SILICON ALLOY

In the prsent paper some of the results of our studies on the formation of cube texture in an iron silicon alloy with silicon content of 3.25% are described. It is found that cube texture in this alloy can be developed either by the process of secondary recrystallization or simply by the process of primary recrystallization. In case of the formation of cube texture by the former process no nucleation process is involved. Nuclei of the (100) [001] orientation are already present after the completion of primary recrystallization, and are surrounded, for most cases, by grains having (110) [001] orientations. Exaggerated growth of cube-oriented grains takes place when the normal growth of other grains are restricted. In case of the formation of a cube texture by primary recrystallization, a spread of cold-rolled cube texture must be present after the last step of cold rolling. Upon final annealing at a low temperature, a recrystallized cube texture by the process of recrystallization-in-situ is obtained. The cube texture may be further concentrated with an increase of final annealing temperature. Basing upon the measurements by the conventional magnetic torque method, the amount of (100) [001] texture is calculated to be over 90%.