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Correlation between mechanical properties and texture characteristics was investigated in a hot-rolled Ti-7333 alloy. After rolling deformation, two strong fiber-textures with 〈100〉 parallel to rolling direction (RD) and 〈110〉 parallel to RD were determined. The mechanism of stress-induced boundary migration mainly controls the nucleation of recrystallized grains holding the similar orientation with the adjacent deformed grains on the bulged grain boundaries. It was revealed that the 〈110〉 fiber-texture with higher Schmid factor (SF) possesses the high deformation ability along RD.

A synchrotron X-ray micro-diffraction based technique, namely differential aperture X-ray microscopy (DAXM), is used to investigate the subgrain evolution in the bulk interior during ex-situ recovery annealing of a lightly deformed Al sample. This is the first 4D DAXM study of recovery. Supplementary TEM observations reveal that DAXM enables proper reconstruction of the microstructure, with the important addition that it is in 3D. The DAXM result provides a direct observation of the 3D microstructural evolution during annealing and confirms that subgrain boundary migration is an important mechanism for subgrain growth, preferentially removing small subgrains. Moreover, it gives new evidence of subgrain coalescence as an alternative mechanism for subgrain growth—some neighboring subgrains are observed to merge due to the decrease of the misorientation angle across certain subgrain boundaries. A possible interaction of the two recovery mechanisms is discussed, as well as the advantage and limitation of the DAXM technique for recovery studies.

Based on the interaction of solid and liquid phases in metallic systems, the paper deals with the properties of grain boundary propagation (migration) in solid-state alloys. Using the effect of surface solid-state dispersion enables to obtain composite materials and brazed joints with a required set of physical and mechanical properties. For the first time, the authors investigate the features of boundary migration in type II systems, in which, in accordance with the thermodynamic criterion σss< 2 σSL, the grain-boundary propagation is not basically allowed.

Effects of the geometrical alignment of an idealized deformation microstructure on the migration of recrystallization boundaries are studied using a phase-field model. A deformation field consisting of two sets of regularly arranged bands is used as an example to mimic typical deformed microstructures, while the migration of both initially flat and circular recrystallization boundaries are considered. The results show that for both cases the local variations in the deformation field affect not only the local shape of the migrating boundary but also the overall distances traveled. It is revealed that boundary migration into heterogeneously distributed energy fields are not uniform neither in space nor time, and can therefore not be expressed by the classic migration model with a uniform migration assumption, even when averaged over the whole boundary and long time.

Recent studies regarding the development of high efficiency grain non-oriented (GNO) electrical steels demonstrate that development of columnar-grained microstructures prior to cold rolling is an efficient method to improve the magnetic behavior of the final product. However, the columnar morphology obtained by annealing of the hot-rolled bands was not developed after further processing by cold rolling and final annealing. Understanding the effects of plastic deformation on the development of such microstructures will help to promote them during the final annealing and improve even more the magnetic behavior of these materials. The present research reports the effects of small plastic deformations (0–25%) and annealing time (10–180 min) on the development of columnar microstructures in GNO electrical steels. The columnar grain growth is explained in terms of the strain induced grain boundary migration (SIBM) mechanism, based on the changes in the grain average misorientation (GAM) maps obtained by electron backscattering diffraction (EBSD).

Fivefold annealing twins (FAT) have been assumed to form by grain boundary migration according to the Ashby model. However, the mechanism of boundary migration lacks experimental support. Moreover, the FAT disintegration process has never been reported. In our experiment, the complete formation and disintegration process of FAT in copper nanoparticles was investigated by in-situ transmission electron microscopy with high temporal and spatial resolution. The results show that FAT formation and disintegration arises from the layer-by-layer migration of twin boundaries, induced by partial dislocation emission. This experimental observation is significant to the basic understanding of twinning mechanisms.

The position of fluid film in journal bearing will change while the journal moving in bearing, which can be named fluid film boundary migration (FFBM). It is usually ignored in the calculation of linear dynamic coefficients. While, the errors brought by this neglection was not ever investigated in detail. In this paper, the influence of FFBM on bearing dynamic coefficients and rotor system dynamic behaviors are investigated. A new perturbation-based model is proposed to take the FFBM into account by modifying the boundary conditions of governing equations. It is then verified by the experimental results and analytical results from previous research. Furthermore, the effects of FFBM on stiffness and damping in two typical journal bearings are investigated. The result indicates that the FFBM has a significant influence on dynamic coefficients of full circular journal bearing but little impact on journal bearing with axial grooves. Moreover, it affects the stiffness and damping more significantly in the cases of large length-to-diameter ratios or small eccentricity ratios in full circle bearing. Finally, the dynamical behavior of a rotor-bearing system with considering the FFBM is also investigated. The result shows that the FFBM of oil film has remarkable influences on the instability threshold and imbalance responses of the rotor system, which should not be ignored. The conclusions obtained in this research are expected to be helpful for the design of full circular journal bearings or rotor-bearing systems.

Grain boundary migration during deformation of nanostructured materials has been reported for a variety of materials and loading conditions. As boundary migration occurs even under cryogenic conditions, it is believed to be mainly mechanically driven, although results suggest thermal assistance. Yet, these contributions could not be separated and the underlying apparent activation energies remain uncertain. Here we present an approach that is capable to determine the average activation energies for mechanically driven boundary migration. While the apparent activation energy is increasing with temperature, below critical temperatures it becomes zero, indicating the existence of an entirely mechanically driven regime.

The effect of strain on the resultant microstructure of an experimental low stacking fault energy Nickel based superalloy containing 24 wt. pct. Co was investigated. Billets subjected to a preliminary heat treatment at 1110 °C were compressed to strain limits of 0.15 and 0.5 at strain rates ranging from 0.1/s to 0.01/s and temperatures at 1020 °C and 1060 °C. The as-deformed microstructures were assessed and characterized using electron backscatter diffraction, as were microstructures corresponding to a super-solvus anneal heat treatment at 1160 °C for one hour. This study sought to identify a critical strain limit at which conditions indicative of Strain induced boundary migration (SIBM) could be effectively triggered for the experimental Ni-based superalloy over a set range of thermal-mechanical parameters. Microstructures corresponding to SIBM were then compared to more extensively deformed billets which contained notable fractions of dynamically recrystallized grains to quantify differences in the length fraction and density of ∑3 twin boundaries of the respective microstructures. Though billet samples deformed to both 0.15 and 0.5 contained notable magnitudes of stored strain energy, microstructures deformed to 0.15 were noted as having maintained larger length fractions of ∑3 twins due to a predominant absence of dynamic recrystallization. Annealed samples originally deformed to 0.15 yielded annealing twin length fractions as high as 59% when compared a sample deformed to the 0.5 strain limit under equivalent thermal-mechanical conditions that resulted in a twin length fraction of 50%. Although samples deformed to the lower strain limit exhibited higher length fractions of annealing twins, samples deformed to the higher strain limit of 0.5 were noted to yield ∑3 densities as high as 0.65 μ m − 1 , whereas the annealed sample deformed under equivalent thermal-mechanical parameters to the 0.15 strain limit produced ∑3 densities as low as 0.32 μ m − 1 .

The pinning effect of adding the microalloying element Mg on the growth of austenite grain for low-carbon steel was investigated in this study. The grain growth pinning behaviour of austenite was observed in situ at high temperature using a high-temperature confocal scanning laser microscope at 1573 K for 300 s. The average austenite grain size was calculated using optical micrograph Leica software. In situ observation showed that the finely dispersed Mg inclusions can inhibit the boundary migration of austenite grains. MgO–MnS is the most effective inclusions for pinning of austenite grain boundaries in Mg-containing SS400, and the ratios of inclusion on austenite grain boundaries to the total inclusion are 43%. In addition, the increase in Mg addition reduces the grain mobility.

The evolution of Σ3n (n = 1,2,3) boundaries in a Ni-Cr-Mo alloy during an aging treatment at 600 °C was investigated based on electron backscatter diffraction (EBSD) measurements. Incoherent Σ3 (Σ3ic) and coherent Σ3 (Σ3c) boundaries were identified using the single-section trace analysis method. The results show that the Σ3n boundary distribution characteristics are changed and that a Pt2Mo-type Ni2(Cr,Mo) superlattice phase precipitates during the aging treatment. Through the analysis and comparison of the average grain diameters measured under the different conditions, the migration behaviors of both the Σ3ic boundaries and random high-angle boundaries (HABs) are found. The migration of the Σ3ic boundaries provides the probability of interaction between Σ3n boundaries. This interaction is responsible for some different types of triple junctions, the increase in Σ9 and Σ27 boundary fractions and interrupted connectivity of the network of random HABs. However, the Σ3c boundaries' consumption caused by the migration of random HABs and the difficulty of forming new Σ3c boundaries lead to the decreased fraction of Σ3c boundaries. The further discussion about the increase in the fraction of Σ3ic boundaries indicates that the generation mechanism of the Σ3ic boundaries during the aging treatment differs from the models applied to recrystallization and subsequent grain growth processes.

We present direct evidence of a network of well-defined ultra-low-angle boundaries in bulk recrystallizing grains of 99.5% pure aluminium (AA1050) by means of a new, three-dimensional X-ray mapping technique; dark-field X-ray microscopy. These boundaries separate lattice orientation differences on the order of 0.05° and thus subdivide the recrystallizing grain into 2–7 μm wide domains. During further annealing the orientation differences decrease and the overall structure become more uniform while the network remains. It is observed that the morphology of the grain boundaries surrounding the recrystallizing grains relate to the intragranular network and effects hereof on the boundary migration is discussed.

Severe plastic deformation effectively produces nanostructured metals. During deformation these structures undergo repetitive dynamic recovery processes, limiting refinement and aspect ratio. Processing tantalum at elevated temperatures by high pressure torsion allows the synthesis of structures with extreme grain aspect ratios of almost ten. Although the overall restoration processes increase with deformation temperature, reflected in enlarged lamellae thicknesses, they are not effective enough to reduce the lamella length at elevated temperatures. Our results indicate that triple junction motion is impeded below a certain temperature while the efficiency of deformation-induced boundary migration diminishes with temperature, allowing to generate such elongated structures.

Deformation twins in magnesium exhibit considerable densities of I1 basal-plane stacking-faults. Since these faults generally transect their host twin, they presumably lengthen concommitantly with boundary migration during twin growth. We investigate this process using atomic-scale simulation for 10 1 ¯ 2 and 10 1 ¯ 1 twinning. It is demonstrated first that the intersection of a stacking-fault with a stationary twin boundary is delineated by a sessile imperfect disconnection. Subsequently, by applying a shear strain, we stimulate twin growth by the passage of twinning disconnections along twin boundaries, and show that these are able to propagate through such pre-existing imperfect disconnections in a conservative manner.

The roughness of grain boundaries in partly recrystallized microstructures has been quantified. Effects of material and processing parameters on the roughening behavior have been statistically investigated. Parameters are sample purity, deformation strain and boundary migration direction in two cold rolled aluminum samples. The results show that particle pinning is not the main reason accounting for recrystallization boundary roughness in the present samples. The roughness is however shown to relate to the deformation microstructure and possible effects of migration rate are discussed.

Electron backscattered diffraction serial image analyses on AZ31 magnesium alloy compressed along RD at different strain levels revealed that twin–twin interactions are found to correlate with mechanical hardening. Four typical twin–twin structures are investigated: (1) Parallel twins with single variant; (2) Interacting twins with single variant; (3) Parallel twins with double variants; (4) Interacting twins with double variants. We studied twin–twin interactions by combining experimental observations and Schmid factor analysis. Due to twins intersecting with each other, the limited growth rate of twins was observed in EBSD maps. The intersection between different twin variant pairs was found to retard the twin growth and promote the nucleation of new twins near intersection region. Besides, “Apparent crossing” twin structure is a limiting case, in which the twin is crossed by a couple of twins, and the interaction region grow slowly. Twin–twin boundary migration is also observed during deformation in this paper, which is considered as an important cause to prohibit twins for further propagate and growth. All these features can be related to twinning-induced hardening.

A new method for quantification of mobilities of local recrystallization boundary segments is presented. The quantification is based on microstructures characterized using electron microscopy and on determination of migration velocities and driving forces for local boundary segments. Pure aluminium is investigated and the results show that even for a single recrystallization boundary, different boundary segments migrate differently, and the differences can be understood based on variations in mobilities and local deformed microstructures. The present work has important implications for understanding of recrystallization boundary migration, and suggests an experimental way forward for how to determine boundary mobilities during recrystallization.

In order to elucidate the predominance of near-Goss grains after Strain-Induced Boundary Migration (SIBM) in electrical steel sheets, the microstructures of grains of orientations close to Goss, D-Cube, and {111}〈112〉 were observed by TEM after temper rolling of 5 % (which is the optimal strain for the development of a strong Goss-type texture) and 9 % reduction (selected to emphasize the differences between orientations and facilitate their analysis). After 5 % strain, the dislocation density seems to be the smallest in the Goss grains. After 9 % strain, this difference in dislocation density is still present but also accompanied by a difference in dislocation arrangement between the Goss grains and the others. These microstructural features are put in regards to some calculations of rotation rates of individual orientations and analyses of slip system activities performed with the Taylor model. The analysis of all these data allow us to establish a strong link between dislocation microstructure and stability of orientation and to conclude that this correlation may be responsible for the favored growth of the near-Goss grains by SIBM during annealing after 5 % temper rolling.

Effects of local variations in the deformation microstructure on subsequent recrystallization are discussed and illustrated by three examples. The three examples consider local variations on different length scales and are: 1. Effects of local variations in the deformation microstructure on the formation of protrusions on migrating boundaries. 2. Effects of an inhomogeneous spatial distribution of second phase particles on growth. 3. Effects of stored energy and orientation variations on recrystallization kinetics.

The recrystallization behaviors of 60% rolled Fe-wt.3%Si and Fe- wt.3%Si-Mn-S alloys containing coarsen MnS particles were observed in temperature range 600°C~1000°C. The activation energy for recrystallization was determined according to an Arrhenius type of relationship. It was found that the activation energy in the temperature range 600°C~750°C was much higher than that in the temperature range 850°C~1000°C. Thermo-mechanical calculation indicates that there are hardly precipitation behaviors of MnS particles in 600°C~1000°C. Fe3C will precipitate below 650°C and Cottrell atmosphere will form just above 650°C, which induces dragging effect against the boundary migration during recrystallization and increase the activation energy. The activation energy determined was about 99kJ/mol or 217kJ/mol in Fe-3%Si alloy and 91kJ/mol or 220kJ/mol in Fe-3%Si-Mn-S alloy for the recrystallization in high temperature range of 850°C~1000°C or low temperature range of 600°C~750°C respectively.

The present paper investigates the potential application of Strain Induced Boundary Migration mechanism on the two different types of surface textures developed after α-γ-α phase transformation annealing, one with preferred cube and Goss orientation at the surface and the other with random surface texture without preferred orientations. It has been demonstrated that these surface texture components grow in across the thickness of the sheet after an appropriate combinations of a critical amount of rolling reductions and an annealing treatment at the recrystallisation temperature.

Semi-processed nonoriented electrical steels are very attractive products whose magnetic properties are significantly improved through annealing treatment in customers plant. The improvement is due to strong Goss texture formation by strain induced boundary migration (SIBM). In order to the effect of temper rolling reduction on the strengthening of Goss texture, temper rolling reduction was changed in the range of 2% to 8%. The annealing times was changed from 10 minutes to 180 minutes. A mechanism of grain growth during SIBM is suggested from our experimental data. In the specimen temper-rolled by 2%, relatively strong {111} texture develops, whereas in the specimens temper-rolled by 4% through 8%, strong Goss texture develops as a result of SIBM during final annealing. It can be found from observed EBSD data that the Goss grains have the lowest stored energy in all temper-rolled specimens, which is confirmed by average image quality value in EBSD measurements. However, for the Goss grains to grow preferentially, stored energy difference between Goss grains and their neighboring grains may have to be higher than a certain critical value.

The detailed microstructure in front of recrystallization boundaries and their migration during annealing were traced using ex-situ electron backscatter pattern maps of one and the same surface area taken after annealing. It is observed that many protrusions/detrusions form on the recrystallizing boundaries. During annealing, the recrystallization boundary segments migrate in a stop-go type of fashion, while protrusions and detrusions alternately form and disappear. The correlation between the protrusions/detrusions and the stop-go type of migration are briefly discussed.

Boundary migration during recrystallization has been followed by an ex situ electron channelling contrast technique, and protrusions/retrusions formed locally on recrystallization boundaries have been quantified. The results show that the motion of recrystallization boundaries is much more complex than generally appreciated. Locally protrusions/retrusions can provide a driving force comparable in magnitude to the driving force from the stored energy in the deformed matrix. The stop–go motion of the recrystallization boundaries is also discussed and related to the formation of protrusions and retrusions.

Effects of segregation of solute atoms and vacancies on migration of antiphase boundaries (APBs) in stoichiometric (Fe-25 at%Al) and Al-rich (Fe-28 at%Al) Fe 3 Al at 673 K have been studied using a phase-field method in which local vacancy concentration is taken into account [Koizumi Y, Allen SM, Minamino Y. Acta Mater 2008;56:5861, ibid . 2009;57:3039]. Boundary mobility ( M ) of APBs having different phase-shift vectors of a/4 and a/2 (hereafter denoted as B 2-APB and D 0 3 -APB, respectively) was evaluated by measuring the boundary velocity of shrinking circular APBs. Similar effects of the segregation on the migration of B 2-APBs were observed in both compositions. Vacancies segregated and Al-atoms were depleted at B 2-APBs in both compositions. Vacancy concentration at B 2-APBs was up to 80% higher than that in the bulk. As a result, the migration of B 2-APBs was greatly enhanced by the vacancy segregation. In contrast, the segregation to D 0 3 -APBs showed a marked composition dependence. Vacancies were depleted and Al-atoms segregated at D 0 3 -APBs in the Al-rich Fe 3 Al, whereas vacancies segregated and Al-atoms were depleted at D 0 3 -APB in the stoichiometric Fe 3 Al. The Al segregation in the Al-rich Fe 3 Al decreased M of D 0 3 -APBs much more significantly than the Al-depletion in the stoichiometric Fe 3 Al. As the APDs shrank, D 0 3 -APBs broke away from the segregation atmospheres and the M increased rapidly in both compositions. A greater increase in the M due to the breakaway was observed in the Al-rich Fe 3 Al than in Fe 3 Al with the stoichiometric composition.

The evolution of cluster of grains with ∑3 n relationship (∑3 n CG) in austenitic stainless steel was investigated by in situ microstructural observations using electron backscatter diffraction (EBSD). The results showed that, after cold rolling with thickness reduction of 6%, ∑3 n CG developed from several existing grains during annealing at 1173 K. As annealing proceeded, ∑3 n CG was growing larger with the so-called strain induced boundary migration (SIBM), and in the meantime, the connectivity of random high angle grain boundaries (HABs) network was interrupted by low ∑-coincidence site lattice boundaries (∑CSLBs) effectively.

The movement of individual boundaries during grain growth after primary recrystallisation in a 96% cold rolled sample of pure nickel has been followed using electron backscatter diffraction maps of the same surface area taken after each of several annealing steps. Particular attention is given to the migration of boundaries with near Σ3 misorientations. During annealing, a small reduction in the length fraction the Σ3 boundaries was observed in the early stages of annealing. Analysis of individual boundaries shows that only those boundary segments with a misorientation angle greater than 4° move during annealing. In addition, the Σ3 boundaries can be divided into two groups: those with misorientations very close to the ideal twin misorientation ('twin type') and those with a larger deviation to the ideal twin misorientation, but still satisfying the Brandon criterion ('neighbour type'). Of these, only neighbour type Σ3 boundaries are observed to move during annealing. Some implications of these o...

An aluminum bicrystal with (001) [100] and (112) [11 1] orientation was deformed by plain-strain compression to a strain of 0.34. The types of slip systems responsible for producing crystal rotations relative to the initial orientations were clarified by the crystal rotation axis method. In the (001) [100] crystal, an affected zone developed along the grain boundary, which revealed a variety of slip systems in operation; the operation of some of these systems could be predicted from the Schmid factor while that of the remaining systems could not. The unpredictable slip systems were activated by the formation of cross slips. After annealing at 400 C for 30 s, recrystallization that occurred was characterized by strain-induced boundary migration. The recrystallized area had the same crystal orientation as that of the affected zone of the (001) [100] crystal. By using the crystal rotation axis method, it was determined that the affected zone was the origin of the strain-induced boundary migration. [doi:10.2320/matertrans.L-MG200952]

The Cu–12 wt.% Fe microcomposite of filamentary composite structure was prepared by heavy cold drawing. The microstructure was observed, and the mechanical properties and electrical conductivity were determined for the microcomposite annealed at different temperatures. Annealing at temperatures lower than 300 °C results in slight decrease in the strength and hardness and a certain increase in the conductivity. Obvious recrystallization occurs in the filamentary structure at higher than 400 °C. The filaments are basically replaced by equiaxial recrystallized grains at higher than 500 °C. The strength and hardness markedly decrease while the conductivity markedly increases with annealing temperatures from 300 to 600 °C. However, the conductivity decreases with annealing temperature from 600 to 700 °C. A suitable matched relationship between the mechanical properties and electrical conductivity can be obtained if the boundary migration of fine recrystallized grains is only restricted within the filaments of the heavily deformed structure during annealing.

The three dimensional x-ray diffraction (3DXRD) concept is shortly described and new experimental updates are highlighted. The potentials and limitation of the 3DXRD method are compared to those of other 3D methods. 3DXRD has been used for in-situ studies of recrystallization and new migration rate results are presented. Migration mechanism for boundary segments surrounding a recrystallizing grain are described and discussed.

The preparation of calcium-deficient hydroxyapatite (CDHAp) beads via immobilization in Ca-alginate hydrogel was studied in current research. CDHAp beads of different shapes were prepared by dropwise adding of aqueous CDHAp/Na-alginate suspension to an aqueous and ethanolic Ca(NO3)2 solutions. The alginate cross-linking rate was modeled via gelling boundary migration experiment. Prepared beads were washed with deionized water and dried. The beads had lost up to 30% of the diameter comparing to the original after drying (24 h, 60 oC).

In general, plastic strain occurs over a certain stress, called yield stress. However, it has been reported that the permanent strain could happen during boundary migrating even under the extremely slight externally applied stress. In this study, we performed dilatometry experiments under the various compressive stresses and measured the amount of recrystallization and growth induced permanent strain. A new empirical constitutive equation was suggested to describe the recrystallization and growth induced plasticity. This equation was verified by comparing the calculated values with dilatometric experimental data under the various compressive stresses.

Effects of the crystallographic misorientation across boundaries between recrystallising grains and the neighbouring deformed matrices are discussed and exemplified by recrystallisation investigations of fcc metals. Classic misorientation observations are reviewed in the introduction, whereas the main parts of the paper focuses on two special boundary migration phenomena observed by in-situ recrystallisation experiments; namely protrusions and facets.

Two types of aluminum bicrystals (Bicrystal 1 and 2) having an asymmetric tilt grain boundary were grown. In Bicrystal I, the orientations of component grains were related to each other by 45° rotation about the normal of the wide surface of the tensile specimen. In Bicrystal 2, although the primary slip planes were symmetric about the grain boundary plane, the component grains were related to each other by 180° rotation about the tensile axis of the specimen. The specimens were deformed to a tensile strain of 0.3 and subsequently annealed. In both bicrystals, deformation bands were not formed symmetrically about the grain boundary. After annealing, no strain induced boundary migration was found. Recrystallization occurred through (111) rotation mechanism. These results were compared with the deformation and recrystallization in aluminum bicrystals having a symmetric tilt grain boundary.

A critical point in the understanding of recrystallization textures is the development of crystallographic orientations of the nuclei. Here an issue, which has been debated much recently [eg. 1], is if nuclei have orientations identical to those of the deformation microstructures from which they originate or not. Traditional nucleation mechanisms like strain induced boundary migration [2] and particle stimulated nucleation [3] operate with nuclei orientations identical to the “parent”deformation microstructure. This is also what is commonly incorporated in recrystallization modeling. However, a number of studies have found recrystallization nuclei in orientations that were not expected from measurements on deformed structures. Some of these results are reviewed and discussed in this paper, and new in-situ results obtained by the 3 dimensional X-ray diffraction (3DXR) method are presented.

The nucleation of recrystallization in deformed and annealed metals is reviewed. The main mechanisms are thought to involve the growth of subgrains by low angle boundary (LAGB) migration in an orientation gradient or the strain induced boundary migration (SIBM) of existing boundaries. Although these mechanisms are reasonably well understood, the details of the dislocation recovery mechanisms which are often required before migration can occur, particularly in metals in which recovery is slow, are poorly understood. Complete experimental investigation of the nucleation event requires a 3-d in-situ technique which will resolve dislocations, and this is not currently available. Although recrystallized grains of orientations not in the deformed structure have been reported, there is as yet no substantial evidence or theory to suggest the creation of new orientations by mechanisms other than annealing twinning. It is concluded that further understanding of the deformed state is required before adequate models of nucleation can be formulated and verified.

Texture formation through strain induced boundary migration (SIBM) was investigated. Temper rolling reduction before final annealing for SIBM was varied between 0 and 26% and grain sizes and textures were measured using EBSD. In the specimen which was temper rolled to 5%, in which grain growth by SIBM occurred most efficiently, a strong Goss component (which was a minor component after rolling), developed during annealing. From the EBSD image quality analysis, it was found that stored energy increased significantly in the Goss component with strain (from 5 to 9 %), whereas it was always relatively small in the D-Cube component ({001}), compared to Goss and g-fibre components. Based on these results, a mechanism of grain growth by SIBM was suggested. Texture evolution during annealing could thus be explained by the hypothesis, speculated from the analysis of orientation stability, that D-Cube grains are associated with more homogeneous dislocations distributions than Goss grains, in which the co-existence of high and low dislocation density zones could favour grain growth by SIBM.

With the 3DXRD microscope it is now possible to follow in-situ the 3D shape of a recrystallizing grain in the bulk of a deformed microstructure. This opens up the possibility of making direct measurements of boundary migration through a deformed matrix. This paper focuses on recrystalliztion in a deformed Aluminum single crystal with initial orientation (112) (Cu).

The development of deformation texture in ferrite has been measured in cold rolled IF steel. This has been compared, in a quantitative way, to the predictions of Taylor models—including those with relaxed constraints—and a finite element model with crystal plasticity constitutive laws. The finite element model gave much better prediction of the overall levels of orientation density but failed to predict the relatively high level of {0 0 1}〈1 1 0〉 texture which occurred at strains greater than about unity. That feature was predicted by relaxed constraint Taylor models. It is argued that that prediction is a coincidence, and either the finite element model cannot readily deal with the intragranular inhomogeneity of deformation in an adequate way, or that factors such as high-angle boundary migration may be important in the development of deformation texture.

In order to clarify the effect of piled-up dislocations on the strain induced boundary migration (SIBM), deformation and recrystallization experiments were performed using an aluminum bicrystal specimen with twin boundary at initial orientation. During the deformation to 20% strain, inhomogeneous deformation took place near the grain boundary (GB). Two kinds of dislocations, edge and screw ones, were piled up against the GB in one component crystal. In the other crystal, edge dislocations were piled up against it. After the annealing, the SIBM was recognized along the original GB. The interaction of the piled-up dislocations was considered to occur at the GB, and it would influence the recrystallization behavior. Since the screw dislocations in one crystal were transmitted during the deformation to the other crystal through the GB because of the special orientation and geometric conditions, they could not be retained stably near or at the GB. In contrast, the edge dislocations introduced into the GB in both crystals were accumulated each other near or at the GB, thereby the component of tilt boundary took part in the original twin boundary. Therefore, it was understood that the SIBM resulted from the annihilation and rearrangement of these dislocations.

This work has shown that submicron grained (∼0.35 μm) structure can be formed by applying equal channel angular extrusion (ECAE) to e=8 at room temperature. In addition, the resulted submicron grained structure is characterized by a random microtexture. Based on the observation, it is suggested that grain subdivision and texture evolution, as well as local boundary migration are the possible mechanisms involved in the formation of submicron grains during severe plastic deformation.

The rate of strain-induced boundary migration (SIBM), which appears during small strains in carbon steel under the critical strain for dynamic recrystallization, was measured through in situ observation at high temperatures. The rate of SIBM measured is much higher than the rate of grain growth without strain. The in situ observation method confirms that SIBM can be initiated by strains as small as 0.015.

International audience; The shear-coupled boundary migration of < 001 > symmetric tilt boundaries is investigated within the framework of an elasto-plastic theory of disclination and dislocation fields. The tilt boundaries are built from periodic partial wedge-disclination dipole arrays, on the basis of their atomistic topography. Non-locality of the elastic response of the adjacent crystals stems from the defected structure of their boundary. Upon applying a shear strain to the bicrystal, couple stresses are generated, which set the disclination dipole array into motion normal to the boundary. In the process, edge dislocation densities with partial Burgers vector lying along the boundary are nucleated, whose glide parallel to the boundary and annihilation produces plastic shear. The misorientation dependence of the shear coupling factor predicted by the model is in full agreement with data from atomistic simulations and experiments. It is found to depend on the polarity and the magnitude of the wedge disclination dipoles composing the grain boundary.

A recrystallization texture with a strong maximum on the α-fibre at {117}〈110〉 what is 12° close to {001}〈110〉 is formed after two subsequent cold rolling and recrystallization steps. During the first recrystallization after a rolling reduction of 90% a texture characterized by a maximum on the γ-fibre and a comparatively strong accumulation on the α-fibre at {116}〈110〉 is developed. The occurrence of these texture components can be explained by subgrain growth and strain induced boundary migration, respectively. Due to nucleation at cementiteparticles the recrystallization texture is weakened and the maxima are broadened in comparison to the deformation texture. The accumulation at {116}〈110〉 provides the nuclei for the recrystallization after the second cold rolling reduction of only 10% when only grains with low stored energy are able to act as recrystallization nuclei so that an orientation selection of near {001}〈110〉 oriented grains takes place.

The process for creating a new recrystallized grain by the bulging out of an existing grain boundary within the deformed structure was recognized by Beck and Sperry and described as strain induced boundary migration, often now as SIBM. For many years SIBM seemed to be accorded less significance than the subgrain growth models for nucleation of recrystallization. However, the importance of SIBM is increasingly recognized, for example in the case of cube texture development in aluminum alloys. There is increasing evidence that high angle boundaries in deformed metals are not only residues of the prior grain structure but may also be generated by the deformation itself. These also participate in the nucleation of recrystallization on annealing and must do so by some form of SIBM mechanism.