Papers by Keyword: Primary Recrystallization

Abstract: The microstructure evolution during the annealing treatment of a recycled copper after cold rolling to total strain of 2.6 was investigated. The cold deformation resulted in the elongation of initial grains along rolling direction and the strain-induced formation of subboundaries. Annealing recovery occurred in the temperature range 100-250 °C. The recrystallized microstructures were observed after annealing at 300-400 °C. The hardness of partially recrystallized copper samples was interpreted in terms of dislocation strengthening. The recrystallization kinetics was estimated according to a Johnson–Mehl–Avrami–Kolmogorov equation using different methods for recrystallized fraction determination, i.e., the fractional softening, the grain orientation spread, and the Kernel average misorientation.

Abstract: The 87% rolling reduction cold-rolled grain-oriented Fe-3%Si steel (Hi-B) was selected as the experimental materials. As the condition of Goss component in primary structure plays a significant role for its abnormal growth in the subsequent secondary recrystallization, static magnetic annealing was used to affect Goss texture and another main texture (111)[112] development in primary recrystallization in this article. It is found that magnetic field annealing can alter the texture development to a certain extent.

Abstract: Data are presented on the x-ray line broadening distribution over the texture of cold-rolled Nb and Mo sheets. The method of generalized X-ray pole figures, which combine texture measurements with X-ray line profile analysis, is employed. The X-ray line broadening is considered as an indicator of residual deformation effects. It was revealed that these effects in cold-rolled BCC metals rise as the grain orientation shifts away from texture maxima towards texture minima. The intensity of X-ray reflections change during annealing at 200 – 500C and this change correlates with the line broadening. The recrystallization texture of BCC metals is dominated by orientations deflected from the peak maxima by 25 – 30 deg. These orientations in the deformed structure have relatively high stored energy. Their volume fraction is sufficient for them to be able to consume most of the deformed matrix.

Abstract: The effects of inter-pass ageing temperature during cold rolling on structure, magnetic properties and mechanical properties of high permeability grain oriented electrical steel was studied. The samples were processed in a single-stage cold rolling to 0.27 mm thickness, with 88 % reduction, without and with inter-pass ageing treatment in order to determine the magnetic properties. To determine the changes in mechanical properties due to strain ageing, the samples underwent overlapped ageing, after pre-strain by rolling, under the same conditions of inter-pass ageing and then were subjected to tensile test. The effect of strain ageing was more pronounced in the thickness of 0.7 mm and the largest variation in yield strength was at 200°C in all evaluated thicknesses. At this temperature the largest amount of {110} orientation after primary recrystallization was also observed, as well as the lowest final grain size and consequently the best results of core loss. The magnetic induction had almost no alterations.

Abstract: The effect of cold rolling reduction on shear band formation and crystal orientation within shear bands and annealing texture were investigated in Fe-3%Si {111}<112> single crystals. Several types of shear bands were observed with different angles to rolling direction, dependent on rolling reduction. As for shear band formation, those with smaller angles were formed earlier and those with larger angles were formed later. Regarding crystal orientation along shear bands after rolling reduction, orientation distribution from the initial became large in accordance with reduction and even exceeded Goss orientation when rolling reduction became larger than 40%. After annealing, however, recrystallized grains along shear bands were mainly Goss grains regardless of reduction. The speculated reason for the dominance of Goss after annealing is that Goss subgrains with less density of dislocations were surrounded by largely deformed areas.

Abstract: The phenomenon of secondary recrystallization in 3%Si-Fe under relatively high cold rolling reduction rate condition has been investigated. The texture of the secondary recrystallized sample under 97.2% cold rolling reduction rate condition consists of {110} orientation, which is quite different from Goss ({110}) orientation obtained under lower cold rolling reduction rate conditions. As a result of Grain Boundary Character Distribution (GBCD) analysis on primary recrystallized texture, {110} orientation has the highest frequency of High Energy (HE) boundary with misorientation angle between 20° and 45°. This result demonstrates that the orientation, which has the highest frequency of HE boundary in primary recrystallized texture, is selected during secondary recrystallization. However, as a result of GBCD analysis based on Coincidence Site Lattice (CSL) boundary, Goss orientation has the highest frequency of S9 (CSL) boundary in the primary recrystallized texture throughout all cold rolling conditions.

Abstract: Grain boundary mobility in preferential growth of cube grains ({100}<001>) 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.

Abstract: Primary recrystallization textures were examined in the 84% and 95% cold-rolled boron-free Ni3Al single crystals with a Goss texture using the electron backscatter diffraction method. It was found that the main components of the textures in the specimens heat-treated at 873K/0.5h had a 40° rotation relationship about <111> to the original, Goss texture. All the eight variants of 40°<111> rotated grains existed. However, the number density is not even but dependent on whether the rotation axis is identical to the normal of slip planes activated during the prior cold rolling. The ratio of the number density among the variants was same in both the 84% and 95% cold-rolled foils. Based on these results, the formation of these 40°<111> rotated grains was explained assuming the modified multiple twinning mechanism where the annealing twinning occurred at the activated slip planes, followed by the subsequent twinning.

Abstract: The evolution of crystallographic texture in a Zr-2Hf alloy has been investigated during deformation, primary recrystallisation and normal grain growth. The as-deformed states (50-90% deformation) are characterized by a major tilted {0001}<1010> texture component and this component is reinforced with increasing deformation. A decrease in the intensity of the tilted {0001}<10 10> component and a continuous increase in the intensity of the tilted {0001}<1120 > component take place during primary recrystallisation. Normal grain growth is associated with the coarsening of grains with the {0001}<1120 > orientation. This texture evolution is interpreted on the basis of the evaluation of the stored energy and the consideration of specific grain boundaries with low energy and/or high mobility.

Abstract: Deformation and primary-recrystallization textures in nickel alloys with some metals (Nb, to 5.4%; W, to 7.4; Re, to 4.1%; Mo, to 9.3%; V, to 10.1%; Mn, to 22.1%; Al, to 12.0% and Cr, to 22.0%) has been studied depending on the content of alloying elements and the rolling temperature. The dependence of the type of recrystallization texture on the component composition of the deformation texture has been established.