Stages Of Recrystallization Research Articles

Calcite recrystallization and its impact on speleothem geochemistry

Speleothems are among the most important archives for past climatic and environmental change. Calcite recrystallization can modify the authigenic structure and geochemical composition of the speleothems and affect the reliability of calcite stalagmites as repositories of authigenic geochemical proxies of past climates and environments. The criteria for distinguishing primary from secondary speleothem calcite, and the conditions (open or semi-closed) of speleothem calcite recrystallization remain poorly understood. Thus, in this study, we investigated the fabric, geochemical composition, and recrystallization dynamics of a partially recrystallized calcite stalagmite (DDH-Z-2) from Didonghe Cave in Shaanxi Province, China, through petrographic observations, fluorescence microscopy, and geochemical analyses (stable isotopes, trace elements, UTh isotopes). We found that: (1) in the DDH-Z-2 stalagmite, open elongated columnar calcite recrystallized into compact elongated columnar calcite. Particulate organic matter and fulvic and humic acids were removed during recrystallization, while aromatic compounds were preserved and became incorporated into the secondary calcite; (2) calcite recrystallization was affected by multiple factors, including external fluid chemistry, primary calcite microstructure, and organic matter; (3) calcite recrystallization occurred under open, fluid-buffered conditions for alteration of the stable isotopes (δ18O and δ13C) and trace elements (Mg, Sr, U). The effect of external fluid composition on trace element (Mg, Sr) composition of secondary calcite varied across the stages of calcite recrystallization. Caution should, therefore, be exercised when using geochemical proxies in stalagmites composed of inclusion-free elongated columnar calcite: such calcite is likely to be recrystallized, and thus record the composition of reactive fluids at the time of recrystallization. Regarding the geochemical system of speleothem diagenesis, the contribution of the parent material and the sources of reactive fluids are key factors to consider.

Evolution and mechanism of recrystallization microstructure and texture in GH3536 superalloy foil and their influence on strength performance

To achieve isotropic strength in GH3536 foil, this study investigated the influence mechanism of initial recrystallization microstructure and texture characteristics of GH3536 superalloy foil with different cold-rolled reduction rates (referring to the reduction rate in thickness) on annealing recrystallization microstructure, including secondary recrystallization microstructure, and texture. This was studied by controlling the cold-rolled reduction rate and annealing temperature, in conjunction with microstructure and texture analysis. Meanwhile, this study clarified the dependency of strength performance on recrystallization microstructure and texture. The results of this study indicate that the Coincidence Site Lattice (CSL) grain boundaries and High Energy (HE) grain boundaries did not show significant superiorities, and were not the primary reasons for the formation of Brass ({011}<211>) and Goss ({011}<100>) textures, as well as secondary recrystallization. Instead, by controlling the cold-rolled reduction rate, the initial recrystallization stage formed a significant quantity and size superiority of α-fiber texture ({110}∥ND) in each grain size range. This led to preferential growth, and even abnormal growth of Brass and Goss grains in subsequent high-temperature annealing processes. The control of the α-deformation fiber texture was identified as the driving factor behind the formation of the initial recrystallization texture due to the cold rolling reduction rate. Cold-rolled processes with a deformation amount greater than 40 % yielded a quantity superiority of α-fiber texture shear bands and an appropriate stored energy advantage. This facilitated the nucleation and effective growth of more α grains, while suppressing the random growth of grains with γ-fiber texture ({111}∥ND). Ultimately, a quantity and size superiority was achieved in the initial recrystallization stage. The tensile strength of GH3536 foil was controlled by grain size and texture. By controlling the deformation amount to approximately 30 %, GH3536 foil was successfully produced with no pronounced orientation texture and isotropic strength.

Numerical modeling of shear band effect on Goss grain recrystallization in electrical steels: Crystal plasticity finite element and phase field modeling

This study investigates the effect of shear band evolution on the nucleation of Goss {110}<001> texture during the primary recrystallization of 3.24 wt% Si grain-oriented electrical steel. Nucleation at the early stage of primary recrystallization of the steel is explored both experimentally and numerically. The experimental approach involves cold rolling the steel specimens to obtain a thickness reduction ratio of 76 % and then applying heat treatment to them at 600 °C for less than 1 min. The numerical simulation employes crystal plasticity (CP) finite element model (FEM) to simulate the plastic deformation induced by the dislocation slips on predefined slip systems and non-crystallographic shear bands during cold rolling. Based on the CPFEM results, the generalized strain energy release maximization (GSERM) model is used to predict the preferential orientation probability of recrystallized nuclei for the steel by considering shear band formation. Subsequently, the microstructure evolution during the early stage of primary recrystallization of the steel is simulated using the phase field model (PFM). The developed CP model successfully predicted shear band activation and evolution in the γ-fibers centered on the {111}<112> texture component. The model also demonstrated that shear bands would be the preferred nucleation sites at the early stage of primary recrystallization because of their high stored energy. Moreover, by coupling with the GSERM model, the PFM could reproduce the nucleation of Goss grains at the beginning of primary recrystallization in shear bands.

Substructure heterogeneity during hot deformation of ferritic stainless steels - Experimental characterization and discussion assisted by a mean-field model

The microstructure evolution of ferritic stainless steels during hot deformation is complex and needs to be finely described. Quantifying the evolution of the misorientation of low-angle boundaries depending on the thermomechanical path is a key point in controlling the recrystallization of such steels. This paper proposes an experimental methodology based on large-scale electron back-scattered diffraction (EBSD) mapping characterization using a Symmetry 2 camera to track the low-angle boundary evolution. Different thermomechanical paths, from 900 to 1100 °C with strain from 0.3 to 0.9, were studied using uniaxial compression tests. Flow stress follows a usual hardening stage, followed by a slight softening regime, mostly attributed to continuous dynamic recrystallization. Distributions of low-angle boundary populations (density vs sub-grain size) are quantified by two populations either near grain boundaries or inside grain bulk; the proportion of sub-grains at grain boundaries increases with strain. This bimodal distribution is made with a probabilistic Gaussian mixture model. These results are discussed using a modified mean-field model of Gourdet-Montheillet. This model is insufficient to capture the transient stage of continuous dynamic recrystallization unless its set of parameters is adjusted to accommodate the saturation of the density of low-angle boundaries near grain boundaries. This saturation is a result of the low-angle boundary density gradients in the grains.

Mineral Mimetic Material Sr-Exchanged Sitinakite of Different Crystallinity: Phase Transformations during Heat Treatment and the Strength of SR Fixation in a Ceramic Matrix.

A simple method for the direct transformation of Sr-exchanged titanosilicate with the sitinakite structure (IONSIV) into ceramic material through cold pressing and subsequent sintering at 1100 °C for 4 h is presented. The temperature transformation of Sr-exchanged sitinakite showed the stages of recrystallization of the material with the formation of Sr-Ti phases matsubaraite (Sr4Ti5[Si2O7]2O8), jeppeite (SrTi6O13), tausonite (SrTiO3), and rutile. Leaching experiments showed the efficiency of fixation of Sr cations in a ceramic matrix; extraction into water does not exceed 0.01% and desorption in 1 M HNO3 solution is only 0.19% within three days. The leaching rates of immobilized Sr demonstrate the structural integrity of the formed phases in the ceramic (2.8 × 10-5-1.0 × 10-5 g/(m2·day). The decrease in the crystallinity of the initial Na-sitinakite, which is achieved by reducing the synthesis temperature from 250 to 210 °C, does not affect the sorption capacity and the fixation of cations in the ceramic matrix. The obtained results confirm the prospect of using inexpensive precursors, titanium ore enrichment waste, for the synthesis of sorption materials.

In-situ observation of restoration of tungsten plate via high-temperature confocal laser scanning microscopy

The restoration of an yttria dispersion strengthened tungsten plate and the corresponding microstructural evolution are investigated through in situ annealing using high-temperature confocal laser scanning microscopy. The geometrically necessary dislocation density and subgrain/grain evolution at each annealing stage are confirmed using the electron backscatter diffraction technique. The microstructure's evolution is divided into distinct stages of recovery, recrystallization, and grain growth based on their characteristic features. During the recovery process, the fomation of subgrains occurs. The primary mechanism of recrystallization nucleation is dominated by the strain-induced boundary migration mechanism, and the subgrains preexisting at grain boundaries are the main nucleation sites.

Monitoring of laser-induced fast recrystallization in SS-316L through synchrotron X-ray diffraction

Laser based heat treatments have multiple applications for local tuning of microstructures. They are particularly relevant in the context of laser-based additive manufacturing (LAM), in order to relieve residual stresses or introduce equiaxed structures through recrystallization. In 316L, high stored energy inherited from the high cooling rates of laser processing creates strong crystallographic textures and stable cellular walls, which challenges the possibility of inducing fast recrystallization. In a first step, we perform here a laser heat treatment on a highly deformed 316L steel, and show that in-situ X-ray Diffraction (XRD) is a viable tool for the monitoring of fast recrystallization. The evolution of Bragg peak width over time is connected to the evolution of dislocation density and grain size, thanks to Electron Back-Scattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM) characterization. X-ray signals are shown to reveal different stages of recrystallization, in particular the development of dislocation cells and the onset of nucleation. This study also demonstrates how local heat sources such as lasers may help designing composite-like materials for grain size, texture and hardness optimization.

Mechanistic insights into the thermal–mechanical aging of the interface of cross‐linked polyethylene/silicone rubber

AbstractCable accessory has the interface formed by cross‐linked polyethylene (XLPE)/silicone rubber (SiR), which is prone to surface discharge and thus causes the failure of cable system. This article conducts the simulated experiment of thermal–mechanical aging on the interface of XLPE/SiR. The interfacial breakdown and dielectric properties under different aging states are analyzed. It is found the interfacial aging process of XLPE can be divided into the recrystallization stage and the oxidation reaction stage. The former contributes to the interfacial roughness and thus the better insulating performance, whereas the latter leads to degradation of interface, and thus the worse insulating performance. In addition, combined with the established electric field model for the interface, the differences between thermal–mechanical aging and individual thermal aging on the interface are discussed. The sample under thermal–mechanical aging reaches the maximum interfacial breakdown voltage later than that under individual thermal aging, but their performance tends to be consistent in the later stage of aging.

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.

A comprehensive study on texture evolution and recrystallization mechanism of Fe-4.5 wt% Si with strong {114}

Improving both the magnetic properties and strength of non-oriented electrical steel used in driving motors of new energy vehicles is a great challenge. In this study, a 4.5 wt% Si non-oriented electrical steel that had a strong {114}<481> texture and exhibited excellent magnetic and high strength, was produced via hot rolling, cold rolling and annealing. The texture evolution of hot-rolled plate with strong Goss and medium strength λ-fiber ({100}<0vw>) was investigated in detail during rolling and annealing. The VPSC model was used to simulate the texture evolution during the rolling process, of which the neff model could satisfactorily explain the classical rotation route of Goss and Cube. At the initial stage of recrystallization, the orientation of the recrystallized grains, characterized by electron backscatter diffraction (EBSD), was closely related to the orientation of the hot-rolled plate and rotation path during the rolling process. This clear evidence indicated that the initial recrystallized grains were oriented nucleation. During the recrystallization process, the characterization of specific orientations by quasi-in-situ EBSD revealed that the unusual {114}<481> was formed by an oriented growth mechanism. Texture evolution during the recrystallization indicated oriented nucleation as an inherent property responsible for the initial recrystallization texture, while oriented growth was influenced by deformed grain size and grain boundary characteristics.

Exploring 4D microstructural evolution in a heavily deformed ferritic alloy

We present a multi-scale study of recrystallization annealing of an 85% cold rolled Fe-3%Si alloy using a combination of dark field X-ray microscopy (DFXM), synchrotron X-ray diffraction (SXRD), and electron backscatter diffraction (EBSD). The intra-granular structure of the as-deformed grain reveals deformation bands separated by ≈ 3–5°misorientation. We monitor the structural evolution of a recrystallized grain embedded in bulk, from the early stages of recrystallization to 65% overall recrystallization through isothermal annealing steps. Results show that the recrystallized grain of interest (GOI) grows much faster than its surroundings yet remains constant in size as the recrystallization proceeds. Isolated dislocations embedded within the volume of the recrystallized GOI are investigated.

Evolution of recrystallization texture in nickel-iron alloys: experiments and simulations

ABSTRACT The present work is aimed at examining the effect of solid solution on the development of recrystallization microstructure and texture in FCC materials where SFE remains unchanged on alloying addition. To elucidate the mechanisms of texture formation during recrystallization, pure Ni and Ni-Fe (20 and 40 wt.% Fe) alloys were investigated. After recrystallization, pure Ni showed a cube and a non-uniform α-fibre texture, whereas the Ni-Fe alloys showed a texture characterised by the rotated cube component, brass recrystallization (BR) orientation, and a non-uniform α-fibre. Addition of Fe to pure Ni has led to some fine differences in the recrystallization texture that have been attributed to the role of highly heterogeneous deformed microstructure in the Ni-Fe system because of alloying. However, in all the cases Cu-oriented grains are prone to early recrystallization due to relatively more heterogeneously deformed regions, whereas deformed grains having orientation <110> || ND have shown slow recrystallization. In all cases, the entire stage of recrystallization is dominated by the formation of annealing twin (Σ3) boundary. The mobility of these twin boundaries plays an important role in the evolution of the recrystallization texture, which in turn, depends on its coherency, i.e. grain boundary plane (K1) of twin boundaries. The mechanism of evolution of recrystallization texture and the role of different deformation features during recrystallization is investigated. The cellular automata simulation technique was used to simulate the recrystallization behaviour of the alloys. The simulation results were used to discuss experimental observations.

Forms of presence, interrelation and genetic significance of Al and Li impurities in quartz of gold deposits of the Darasunsky ore field (Eastern Transbaikalia, Russia)

Research subject. The distribution regularities of Al and Li impurities in gold-ore quartz. Materials and methods. The quartz of the Darasun, Teremkinskoye and Talatuy gold deposits of the Darasun ore field was studied. The gross contents of Al and Li impurities in quartz were determined by the LA-ICP-MS method; substitutional Al impurity concentrations were studied by the EPR method. The forms of Al impurity in quartz were determined based on the results of studying its behavior during material recrystallization. The genetic significance of Al and Li impurities in quartz was estimated taking into account the genetic information obtained during the study of the distribution of substitutional Al and Ti impurity concentrations. Results. It was found that Al is present in quartz in two main forms, i. e., as a substitutional Al impurity and Al complexes localized in the areas of high mineral defectiveness. Li+ ions are located in the structural channels of the mineral, serving as compensating ions for both Al impurity forms. The composition of Al complexes is assumed to include three Al3+ ions and one H+ or Li+ ion. Two stages of quartz recrystallization occurring at different temperatures of mineral formation were identified. The first, low-temperature stage leads to quartz enrichment with substitutional Al impurities. The second, high-temperature stage causes the decomposition of Al complexes. The recrystallization stages can be identified by the type of relationship between the gross concentrations of Al and Li. The increased content of Al impurity in ore quartz was found to be related to the presence of a large number of Al complexes. An assumption is made that these complexes formed during mineral crystallization from solutions with a high content of metal ions. Conclusions. The results obtained indicate that high Al impurity concentrations can serve as a genetic sign of ore quartz. At the same time, the decomposition of Al complexes during quartz recrystallization should be taken into account. A method for estimating the initial concentration of Al complexes is proposed, which is a more reliable genetic indicator.

The impact of annealing on microstructure of cold rolled steel plates detected by eddy current method

ABSTRACT Eddy current (EC) is a non-destructive method, which plays an important role in the quality inspection sector of various metal industries. It has been used for a wide range of inspection purposes, such as detecting cracks and defects, and inspecting the coating quality. The EC method can also be utilised in the material and microstructure characterisation of engineering steels and alloys. In this study, the EC method is used to detect the microstructural changes during the annealing of a cold rolled steel plate. To support the EC findings, the electromagnetic results are compared with the hardness measurements and the microstructure observations. The comparison proves that the EC method is able to separate recovery and recrystallisation stages, and extract useful information from the changes in the microstructure at various recrystallisation levels.

Recrystallization and texture evolution of cold pilgered FeCrAl cladding tube during annealing at 700 °C∼1000 °C

FeCrAl alloys are being developed as potential accident-tolerant fuel cladding materials for the light water reactors due to significantly improved steam oxidation and good mechanical properties at high temperatures. In this study, the recrystallization and texture evolution of the cold pilgered FeCrAl cladding tube was investigated by means of hardness measurements and electron backscatter diffraction (EBSD) during annealing at 700∼1000 °C. The partially recrystallized maps were deconstructed into deformed, recovered, and recrystallized grain fractions based on the critical internal misorientation angle. In the early stages of recrystallization, cold pilgered cladding tubes contained a mixture of discontinuously recrystallized {111}<110> newly nucleated grains and heterogeneous deformed 〈110〉 orientation grains. The deformed microstructural inhomogeneity state could be explained based on the Taylor factor. The rate of recrystallization increased with increasing annealing temperature, which was described by the Johnson-Mehl-Avrami-Kolmogorov equation. The cladding tube showed slow recrystallization kinetics and thermally stable grains due to the pinning of the grain boundaries by the Laves precipitates. The dominant α-fiber decreased and γ-fiber increased with increasing recrystallization fraction in the cold pilgered tubes. The high area fraction and stable γ-fiber would be beneficial to the processability of the cladding tube.

Dual-effects of carbon doping on the recrystallization kinetics of the Cantor alloy during mid-temperature annealing

In this study, the comprehensive effects of carbon doping on the recrystallization process and the corresponding mechanical performance of the Cantor alloy during mid-temperature (700 °C) annealing were investigated. In the early stage of recrystallization, i.e., before 7 min annealing, abundant M23C6 carbides form preferentially along deformation bands and hence accelerate recrystallization process by providing dense heterogeneous nucleation sites. The fast consuming of the stored defects by recrystallization in this stage leads to the drastic decrease of strength but the regain of ductility. Detailed characterization on the precipitation behavior further shows that the initial fine carbide (≤10 nm in size) firstly enriches in carbon only, and then gradually grows to perfect M23C6 as controlled by the diffusion of Cr. In the later stage of recrystallization, e.g., after 7 min annealing, these carbides coarsen and Zener-pin grain boundaries from further migration, which in turn suppress the overall recrystallization process. In this stage the mechanical properties vary slightly as a result of the balance between the slowly deceased amount of hard non-recrystallized regions and the slowly increased carbide volume fraction.

Hot deformation behavior and comparison of different constitutive models of as-cast ER8 steel

To facilitate the numerical simulation of plastic deformation and the determination of thermal deformation process parameters of as-cast ER8 steel, isothermal thermal compression test of ER8 steel was carried out, and the flow stress curves of ER8 steel at high temperature was obtained. The selected deformation temperature was 1173–1523 K and strain rate was 0.001–0.1 s−1. On this basis, three different constitutive models were established and compared. The results show that the flow stress curves of ER8 steel can be divided into two stages, namely work hardening-dynamic recovery stage and dynamic recrystallization stage. The traditional Fields-Backofen model was modified to predict the flow stress at different deformation temperatures. According to the error analysis, the AARE levels of the modified Fields-Backofen model and the strain-coupled constitutive model are the same, while the AARE of the physically‑based constitutive model are smaller. The modified Fields-Backofen model cannot reflect the softening of dynamic recrystallization on the flow stress curves during high temperature deformation, while the strain-coupled constitutive model and the physically‑based constitutive model can. In terms of modeling difficulty, the modified Fields-Backofen model is the easiest to model, followed by the strain-coupled constitutive model, while the physically‑based constitutive model is relatively complex to model.

Rapid Visualization of Microstructural Evolution during Hot Strip Rolling Using Phenomenological Models and the Laguerre–Voronoi Diagram

Microstructural evolution during hot rolling, which is complex and in a state of the black box, has a significant impact on the microstructure and mechanical properties of steel products. Herein, a rapid methodology is developed to track and visualize the evolution of the microstructural state, and a novel approach coupled with phenomenological recrystallization kinetics is proposed to calculate grain size and its distribution by considering the effects of the size, shape, and mixed fraction of nonrecrystallized grains, and by using the Laguerre–Voronoi diagram, the microstructural morphologies are reconstructed. Based on the proposed approach, the variations of the recrystallization fraction, grain size, and its distribution with time during rolling are analyzed, and the microstructural features in various recrystallization stages are discussed. Additionally, this strategy is demonstrated to be time efficient.

Electrocatalytic Cascade Selective Approach to 3-Aryl-2'H,3H,4H-Spiro{Furo[2,3-с]Chromene-2,5'-Pyrimidine}-2',4,4',6'(1'H,3'H)Tetraones and Its Automatic Screening Docking Studies

The general electrocatalytic cascade approach was found to medicinally relevant spirobarbituric 2,3-dihydro-4H-furo[2,3-c]chromen-4-one scaffold. This new electrocatalytic fast and efficient reaction of benzylidenebarbiturates and 4-hydroxycoumarin in alcohols in the presence of alkali metal halides as mediators in an undivided cell results in the formation of the substituted unsymmetric spirobarbituric 2,3-dihydro-4H-furo[2,3-с]chromen-4-ones in 72–83% yields. This general and efficient approach avoids traditional recrystallization and chromatographic purification stages. According to screening molecular docking data, all synthesized compounds may be prominent for different medical applications, such as control pain, breast cancer therapies, and treatment of obesity, epilepsy, hypertension, cardiovascular disease and diabetes.

Formation of η-oriented shear bands and its significant impact on recrystallization texture in strip-cast electrical steel

The evolution of shear band (SB) and texture in strip-cast electrical steel was studied in order to investigate the crystallographic character of SB and its influence on recrystallization texture. Shear deformation in the form of SB played an effective role in tailoring the local lattice rotation to accommodate heavy deformation in the case of inhomogeneous deformation under conditions of initial coarse grain in strip-cast electrical steel. During rolling process, η-oriented SBs appeared at different stages of deformation as a result of geometric softening. Cube-oriented SB was mainly retained from initial exact Cube grain at early stage of shear deformation and Goss-oriented SB was newly developed during the formation of γ-fiber matrix after heavy deformation. {210}<001> SB formed as a transition form among different SBs. Crystal rotation inside SB, SB dimension and SB boundary misorientation progressed in proportion to cold rolling reduction. It is demonstrated that crystallographic direction of SBs tended to be parallel to <001> under the driving force of reduction in stored energy to maintain relatively quasi-stable state. Low orientation gradient as well as relatively low density of dislocations was developed within SB region, while high orientation gradient formed between SB region and surrounding matrix. Interestingly, the η-oriented cell blocks inside SBs provided preferential nucleation sites for Goss and Cube texture at early stage of recrystallization, which significantly contributed to beneficial recrystallization texture in a manner of texture inheritance and superior magnetic properties (B50 was as high as 1.81 T, and P1.5/50 was as low as 4.0 W/kg).