Stages Of Recrystallization Research Articles

Spatially Inhomogeneous Recrystallization in Ferritic Stainless Steels

The kinetics of static recrystallization in cold rolled ferritic stainless steel sheet tends to slow drastically over the last 10-20% of recrystallization. This has its origins in both the microstructure (deformed grain shape, precipitates) and in the local deformation texture. In this work we have sought to provide a physical explanation for the slow last stages of recrystallization through a texture dependent JMAK model which is informed by the microstructure of the partially recrystallized microstructure. The geometrical assumptions made in developing this JMAK model have been compared to phase field simulations using experimental observations as the source of their starting configuration.

Microstructural Evolution during Recrystallization of Magnesiun Alloys

Microstructural evolution during the annealing of cold rolled Mg, Mg-1.5Nd and Mg-3Y sheets has been examined. The experimental results show a significant difference in recrystallization kinetics and grain growth between pure Mg and Mg-RE alloy sheets. Pure Mg sheet shows rapid recrystallization and grain growth, whereas recrystallization is considerably retarded in the Mg-RE alloys. Although recrystallized grains which are triggered at shear bands in the cold rolled pure Mg sheet show a relatively weak texture with a basal pole split into the sheet rolling direction, rapid grain growth is accompanied by re-strengthening of the basal-type texture. In contrast, a weak texture appears in the early recrystallization stage in Mg-RE alloys and is retained during annealing due to retarded recrystallization and grain growth.

冷間圧延された A1050アルミニウムにおける回復，再結晶過程初期の同一視野 EBSD 組織観察

冷間圧延された A1050アルミニウムにおける回復，再結晶過程初期の同一視野 EBSD 組織観察

冷間圧延を施した Al-Mg-Si 合金の再結晶挙動

Recrystallization processes in Al-Mg-Si alloys after cold-rolling at 30 to 95% reduction rates were observed on the same area in specimens during annealing at 673 K. Together with the results reported in the previous studies recrystallization phenomena are summarized for aluminum alloys in 6000 series in which dislocation cells are formed by deformation. Strain induced grain boundary migration is an apparent phenomena, which is caused by growth of dislocation cells formed near prior grain boundaries. When subgrains surrounded by low and high angle boundaries are formed during annealing from dislocation cells, the high angle boundaries migrate with invading the neighboring subgrains, and with remaining the area surrounded by the low angle boundaries. In the area swept by the high angle boundaries, orientation gradient is quite low, less than 1 degree, while in the remained area, orientation gradient is relatively high. Crystallites, which grow into recrystallized grains, are composed of such areas with low and high dislocation densities in the early stage of recrystallization. The area with relatively high dislocation density is invaded by other recrystallized grains and disappears, as a result the area with low dislocation density becomes recrystallized grains surrounded only by high angle boundaries.

Crystal–plastic deformation and recrystallization of peridotite controlled by the seismic cycle

Deformed peridotites from the Balmuccia complex, Northern Italy, have been investigated by light and electron microscopy (SEM/EBSD, TEM). The peridotites show a heterogeneous and partly recrystallized microfabric associated with cataclastic shear zones. Intracrystalline deformation microstructures (undulatory extinction, crinkly deformation lamellae, deformation bands, kink bands) and recrystallized grains along intragranular zones in large original grains record a sequence with an initial stage of inhomogeneous glide-controlled deformation in the low-temperature plasticity regime associated with brittle deformation and a subsequent stage of recovery and recrystallization. The microstructural evidence of deformation of olivine in the low-temperature field indicates high stresses on the order of several hundred MPa and accordingly high strain rates. Subsequent recovery and recrystallization requires decreasing stresses and strain rates, as there is no evidence for a complex thermal history with increasing temperatures. A locally occurring foam structure in aggregates of recrystallized olivine indicates grain growth at very low differential stresses at a late stage. Such a stress history with transiently high and then decaying stresses is characteristic for coseismic deformation and postseismic creep just below the base of the seismogenic zone. The associated occurrence of pseudotachylytes and microstructures generated by crystal-plastic mechanisms is explained by semi-brittle behavior at transient high stresses and strain rates during coseismic loading at depths, where during postseismic relaxation and in interseismic periods the rocks are behaving by crystal-plastic flow. The consideration of high-stress deformation and subsequent recrystallization processes at decaying stresses in peridotites is especially relevant for earthquake-driven deformation in the mantle.

Nucleation of Recrystallization in Fine Grained AA3104 Alloy Analyzed by SEM and TEM Orientation Mappings

This paper describes nucleation and grain coarsening at very early stages of recrystallization in AA3104 aluminum alloy containing complex structure of second phase particles. Measurements of individual sub-cell orientations in ECAP-processed and slightly annealed structures were possible by using TEM-based orientation mapping in combination with recrystallization carried out in the microscope. The results were compared with those obtained by SEM/EBSD system. The investigation shows that the 40o<111>-type relation occurs rarely, and the rotation axes of misorientations between deformed and recrystallized areas were strongly scattered. Grouping of the misorientation axes near the <012>, <221>, <112> and <110> crystallographic directions was noticeable.

Effect of Ultrahigh Straining on the Evolution of Cube Texture ({100}<100>) in High Purity Nickel

The effect of ultrahigh straining on the evolution of cube texture in high purity nickel (99.97%) processed by Accumulative Roll Bonding (ARB) is investigated in the present study. Fully recrystallized nickel sheet having average grain size of 28 μm is deformed by ARB to the strain levels of εeq=3.2 and εeq=6.4 corresponding to 4 and 8 cycles of ARB processing, respectively, and subsequently annealed at different temperatures. The 8 cycle ARB processed material consistently shows much higher cube volume fraction as compared to the 4 cycle processed material after different annealing treatments. Almost 100% cube volume could be obtained in the 8 cycle processed material after annealing at 800°C. The development of extremely sharp cube texture in the 8 cycle processed material could be attributed to the oriented nucleation of cube grains at early stages of recrystallization and subsequent growth of these grains. The results indicate that ultrahigh straining could be useful for applications requiring near perfect cube texture such as substrates for coated superconductors applications.

Annealing twins in a multifunctional beta Ti-Nb-Ta-Zr-O alloy

The grain boundary character distribution and annealing twins in a multifunctional β-type Ti-23Nb-0·7Ta-2Zr-O alloy having a stable bcc phase structure are investigated by electron backscattering diffraction (EBSD). The results show that the coincident site lattice (CSL) boundaries, including Σ3 and Σ11 twin boundaries mainly form at the early stage of recrystallization. {112}〈111〉 and {332} 〈113〉 annealing twins are observed to occur in the completely recrystallized Ti-23Nb-0·7Ta-2Zr-O alloy.

Petrology of HP metamorphic veins in coesite-bearing eclogite from western Tianshan, China: Fluid processes and elemental mobility during exhumation in a cold subduction zone

A petrological study was carried out for high pressure (HP) veins which cut through the host coesite-bearing eclogites at Habutengsu–Kebuerte in western Tianshan, China. The results place constraints on the origin and property of metamorphic fluids during subduction-zone metamorphism. Omphacite-, clinozoisite- and quartz-dominated veins occur on centimeter to meter scales within lens-shaped and layered eclogites, or cutting into the country rocks of garnet phengite schists. Coesite-bearing eclogites mainly consist of fibrous fine-grained omphacite and porphyroblastic garnet, with minor amounts of amphibole (mainly barroisite), clinozoisite, white mica (mainly paragonite) and rutile. The veins are pronouncedly coarse-grained compared to the host eclogites and commonly consist of quartz, clinozosite, rutile, white mica (phengite and paragonite) and garnet, with or without omphacite, titanite, apatite, carbonate (mainly dolomite) and glaucophane. Fluid inclusions are abundant in vein omphacite, titanite and apatite, but are rare in the equivalent minerals of host eclogites. Rounded vein garnets usually occur close to the sharp interface of vein and host eclogite. Omphacite in the veins is characterized by its euhedral form surrounded by quartz, or coarse bladed aggregates in contrast to the fibrous or patchy one, suggesting dynamic recrystallization in the host rocks. Omphacite in both veins and host eclogites has similar jadeite contents (Jd40-50), indicating formation at eclogite-facies metamorphic conditions. Vein phengite uniformly contains certain amounts of Ba with maximum BaO content of 3.16–4.25wt.%, suggesting that Ba was mobilized during the exhumation of UHP rocks. Specific textures of vein minerals, such as the enclosure of magnesite (or calcite) in dolomite, rutile in titanite, and the occurrence of zoned Ba-rich phengite, indicate the chemical variability of channelized fluids over time. Based on Zr content in rutile and the presence of paragonite, omphacite, phengite, glaucophane as well as the little deformed textures of HP veins, it is estimated that the vein-forming fluids would flow at about 1.3–2.1GPa and 540–580°C, corresponding to the stage of retrograde eclogite-facies recrystallization during exhumation of the UHP eclogites that formed at peak P-T conditions of >2.7GPa and 460–520°C. The HP veins occur as a consequence of a regional tectonothermal event, triggering breakdown of lawsonite within the UHP eclogites. Based on the petrology of vein minerals, it is inferred that the HP fluids were enriched in Si, Ca, Na, Al and Ba. This suggests that these elements could be mobilized during the retrograde metamorphism of UHP eclogites in a cold subduction zone. Coeval pervasive flow of HP metamorphic fluids through the UHP eclogites at this stage may be an important process to eliminate most mineralogical evidence of the UHP metamorphism.

Analysis of Micro-texture during Secondary Recrystallization in a Hi-B Electrical Steel

The understanding of Goss texture in Hi-B electrical steels possesses significant industrial and academic value, thus attracts worldwide attention. The prevailing models for sharp Goss texture formation during secondary recrystallization are CSL (coincident site lattice) boundary theory and HE (high energy) boundary theory. These theories stress the key factor of preferred growth and the difference between them only lies in the specific selection manner. This work examined the texture gradient in primarily recrystallized sheet and demonstrated its possible influence on the formation of secondary grains, and then determined the micro-texture during different stages of secondary recrystallization using EBSD (electron back-scattered diffraction) technique, finally analyzed a special type of secondary grains with near Brass orientation, which were detected in the later stage of secondary recrystallization, and discussed its origin and effect in terms of surface energy effect. The results indicate that texture gradient in primarily recrystallized sheet will lead to a multi-stage formation of Goss texture, namely, early stage of secondary grains with various orientations in subsurface region, intermediate stage of preferred growth of Goss grains into center layer and re-grow back to the surface and the final stage of Goss grain growth by swallowing slowly the island grains with the help of H 2 atmosphere.

Localized Recrystallization Induced by Subgrain Rotation in Sn-3.0Ag-0.5Cu Ball Grid Array Solder Interconnects During Thermal Cycling

The evolution of microstructures and grain orientations of a Pb-free solder interconnect during thermal cycling significantly affects its mechanical properties and failure modes. Thus, Sn-3.0Ag-0.5Cu ball grid array assemblies were subjected to thermal cycling to study the thermomechanical responses of the solder interconnects. The orientations and microstructures of the solder interconnects were studied by optical microscopy with cross-polarized light and scanning electron microscopy with an electron backscattered diffraction analysis system. Localized recrystallization behavior was observed in Pb-free solder interconnects during thermal cycling. Closer examination of the very early stage of recrystallization in the same solder interconnect revealed that the subgrains appeared before the formation of the recrystallized grains, and the orientations of the small recrystallized grains separated by high-angle grain boundaries evolved from the initial orientations by subgrain rotation. The localized recrystallization produced fine-grained microstructures during thermal cycling, providing an additional deformation mechanism for the solder interconnects, i.e., grain boundary sliding, which would have been impossible prior to recrystallization. The grain orientation has a strong effect on damage generation and the subsequent failure mode; initiation and propagation of cracks could be facilitated by the intrinsic anisotropic thermomechanical responses of the differently oriented grains, leading to a change in the crack propagation path and corresponding failure mode.

Microstructural refinement and mechanical properties of direct extruded ZM21 magnesium alloys

Cast ZM21 magnesium alloys were subjected to symmetric extrusion at four different temperatures (200, 250, 300 and 350 °C) with three extrusion ratios of 4:1, 9:1 and 16:1, respectively. The effects of extrusion parameters such as temperature and extrusion ratio were studied by optical microscopy, X-ray diffraction (XRD) and tensile test. The optical micrographs exhibited various stages of recrystallization, i.e., partial to full recrystallization influencing mechanical properties to good extent. Higher extrusion temperature resulted in coarse grains, whereas finer grains were obtained at higher extrusion ratios. Ultimate tensile strength of this alloy was increased from 160 MPa to 316 MPa after extrusion at 250 °C with an extrusion ratio of 9:1.

The dynamic and quasi-static mechanical response of three aluminum armor alloys: 5059, 5083 and 7039

Abstract The mechanical response and microstructural evolution of aluminum alloys 5083, 5059 and 7039 was examined in compression and shear in both the quasi-static (0.001 s −1 ) and dynamic (≈2000 s −1 ) strain rate regimes. Electron Back Scattered Diffraction was utilized for detailed post-mortem analysis of the specimens following loading. The mechanical responses in shear were found to be strain-rate sensitive. At the slowest strain rates, all of the alloys had relatively large volumes of highly deformed material with 5083 and 5059 having the largest shear affected volumes. The dynamic strain rate test samples all formed highly compact shear localized volumes across the sheared zone with 7039 consistently displaying the narrowest shear regions. The morphology of these shear bands, along with the limited hardening during deformation, indicate a mechanism change at the higher strain rates. Higher resolution orientation image mapping has shown that between the three alloys there are varying degrees of crystallographic order within the shear bands. Transmission electron microscopy revealed various stages of dynamic recrystallization were present suggesting that while low strain rate deformation is controlled by dislocation multiplication and glide, high strain and strain-rate deformation is influenced in part due to mechanical recrystallization.

Orientational Analysis on Static Recrystallization at Tension Twins in AZ31 Magnesium Alloy

The deformation depends on twinning in Mg alloy, and twins will be the dominant recrystallization nucleation site. Tension twinning proceeds much more easily than compression twinning since its volume fraction is much higher than that of compression twins, which may have a promotive effect on the recrystallization to a certain degree. Based on the previous research on the static recrystallization at compression twins, the evolution of microstructure and texture in AZ31 magnesium alloy during its static recystallization at tension twins was further investigated; and the orientational characteristics of new grains formed at tension twins in the early stage of static recrystallization were analyzed by EBSD technique. The results showed that the strong basal texture was retained and weakened with no new texture component being detected during annealing. New grains were observed to nucleate preferentially at the intersections of tension twin variants or the intersection between tension twins and compression twins. Their orientations are relatively random and are strongly scattered from those of original tension twins or compression twins. A comparison of the recrystallization at tension twins and compression twins was further made.

Modeling the crystallographic texture changes in aluminum alloys during recrystallization

The evolution of crystallographic texture during recrystallization annealing is affected by the hot and cold rolling parameters. A 6016 Al alloy with various hot band textures was subjected to conventional rolling and short time annealing at elevated temperature. Asymmetric rolling with differential circumferential velocities of the top and bottom rolls was applied to the aluminum alloy under investigation to modify the hot rolling texture. The presence of large constituent particles enforces strain heterogeneities during cold rolling. The influence of particles on the development of recrystallization textures is discussed based on the experimental data and the results of crystal plasticity simulations. A recrystallization model based on nucleation and growth selection is presented. The driving force for nucleation was accounted for by applying continuum mechanics crystal plasticity models, which allow calculation of the stored energy of plastic strain for specific orientations of the polycrystalline aggregate and for the strain mode under consideration. Crystal misorientations of type 〈1 1 1〉 40° were attributed to enhanced mobility during the growth stage of recrystallization.

The geobarometric significance of plagioclase in mantle peridotites: A link between nature and experiments

Few previous studies on orogenic plagioclase peridotites, and recent low-P subsolidus experiments on lherzolites ( Borghini et al., 2010; J.Petrology 51, 229–254) have revealed that the composition of plagioclase is a marker of varying P conditions in mantle peridotites. Here we confirm this inference, by comparing microstructural–chemical features observed in natural plagioclase-facies recrystallized lherzolites from the External Liguride ophiolitic Unit (EL, Northern Apennine, Italy) with the results of previous ( Borghini et al., 2010) and new (this study) experiments on fertile lherzolite with the same bulk composition. Detailed microanalytical work and textural observations on the EL lherzolites revealed systematic chemical zoning in texturally associated plagioclase and pyroxene neoblasts. Anorthite-reverse zoning in plagioclase is coupled to Al, Na and Ca core-rim variations in granoblastic ortho- and clinopyroxenes, documenting two major stages of equilibration within the plagioclase-facies stability field. Consistent chemical variations in minerals are found in subsolidus experiments on fertile lherzolite in the pressure range 0.25–0.8 GPa. Results of experiments were fitted by multiple least-squares regression analysis to derive an expression for anorthite isopleths as a function of P and T in fertile lherzolites. Application of this equation to the EL lherzolites provided equilibrium pressure of 0.7 and 0.3 GPa for the two recrystallization stages, indicating exhumation from about 22 to 9 km depth. Results of combined experimental work and microstructural–chemical data on natural plagioclase lherzolites, highlight that the composition of plagioclase varies significantly in a rather narrow pressure range, and the shallow (< 1 GPa) P-T evolution of mantle peridotites can be therefore successfully traced by combining chemical zoning in plagioclase and geothermometric investigations on texturally associated pyroxenes. Experimentally-derived Na-Ca partitioning between plagioclase and clinopyroxene can be used to test the attainment of chemical equilibrium in neoblastic plagioclase-bearing mantle assemblages, thus enlarging the applicability of this approach in equilibrated plagioclase peridotites of different origins.

Evolution of recrystallization texture in a 0.78 wt.% Cr extra-low-carbon steel after warm and cold rolling

The detailed evolution of microstructure and microtexture during the annealing of warm-rolled (WR) and cold-rolled (CR) 0.78 wt.% Cr extra-low-carbon steels was studied via electron back-scattering diffraction (EBSD). The partially recrystallized maps were deconstructed into deformed, recovered, newly nucleated and growing grain fractions using a newly developed procedure. In the early stages of recrystallization, the WR samples contained a mixture of discontinuously recrystallized {1 1 1}〈1 1 2〉 newly nucleated grains and previously recovered {1 1 1}〈1 1 0〉 growing grains. During the later stages of annealing, continuous recrystallization was the predominant mechanism with the strengthening orientations confined mostly to the α-fibre at ∼ ( 1 1 2 ) [ 1 1 ¯ 0 ] . Conversely, during the annealing of the CR samples, discontinuous recrystallization took place, with the newly nucleated and growing grain fractions consisting mostly of {1 1 1}〈1 1 2〉 orientations.

Deformation and dynamic recrystallization in copper at different deformation rates in Bridgman anvils

An analysis of structural changes taking place in copper upon deformation by shear under pressure has been performed using the Zener-Hollomon formalism. This analysis has shown that the temperature—strain-rate limits of the stages of structural states are independent of the rate of the anvil rotation. It has been demonstrated that the size of structural elements depends on the temperature-compensated rate of deformation. The use of a low rate of the anvil rotation has allowed detecting a cyclic character of dynamic recrystallization upon shear under pressure. A leading growth of some grains occurs during postdynamic recrystallization if the deformation is stopped at the stage of partial dynamic recrystallization or at the stage of complete dynamic recrystallization when the recrystallization cycle is not complete after the end of deformation.

Defining recrystallization in pilgered Zircaloy-4: From preferred nucleation to growth inhibition

Pilgered Zircaloy-4 was subjected to recrystallization annealing at 650 °C: temperature sufficient for primary recrystallization but inadequate for noticeable competitive grain coarsening. Associated microstructural developments were monitored through bulk and microtexture measurements. The deformed microstructure had two, generalized, types of grains: fragmenting/deforming and non-fragmenting/non-deforming. The former had higher stored energy of cold work and defined the early recrystallization stages through preferred nucleation. Non-fragmenting grains, on the other hand, did not contribute directly to recrystallization; but provided significant growth inhibition or pinning to the recrystallized grains. A combination of these two mechanisms defined the recrystallization behavior of pilgered Zircaloy-4.

Effect of Magnetic Field Direction on Texture Evolution in Cold-Rolled IF Steel Sheet at the Initial Stage of Recrystallization

Sheets of cold rolled (76%) IF steel were annealed at 650°C for 30min under a 12-tesla magnetic field. During the magnetic field annealing, they were placed at the center of the applied field respectively, being oriented differently with respect to the magnetic field direction. The results show that the high magnetic field annealing prevents the evolution from deformed {111}&lt;110&gt; texture component to recrystallized {111}&lt;112&gt; texture component at the initial stage of recrystallization. For the field annealed specimens, altering the specimen orientation to the magnetic field direction during annealing does not change the final annealing textures. The intensity of main {111} texture components presents a similar periodic variation with respect to the specimen orientation to the magnetic field.