Recrystallization Texture Evolution Research Articles

On the Relationship between Thermomechanical Processing Parameters and Recrystallization Texture in AA1100 Aluminum Alloy

In this study, 48 hot-rolling processing conditions were designed to investigate the influences of thermomechanical processing parameters on the recrystallization behavior and texture development. The hot-rolling experiments were conducted using the thermomechanical simulator Gleeble 3800 at temperatures of 275, 300, and 350 °C with strain rates of 5 and 90 s−1 up to 60 and 85% reduction. The microstructure and texture analysis were measured by using the EBSD technique on a large area. Experimental results show that the Cube component maintains a volume fraction between 10% and 20%, below the 40% recrystallization fraction, but the volume fraction of Cube significantly increases between 20% and 50% above the 40% recrystallization fraction. However, the fractions of Rotated Cube (RC) and Goss components remain below 10%.

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.

Recrystallization behavior and texture evolution during annealing of cryogenic-rolled 3003 aluminum alloy

Heterostructure materials have attracted much attention owing to their excellent strength-ductility synchronization. In this work, a heterogeneous structure consisting of coarse grains and ultrafine grains was developed in 3003 aluminum alloy by cryogenic rolling and short-time annealing. The recrystallization behavior and texture evolution in cryogenic-rolled 3003 aluminum alloy were investigated by using X-ray diffraction and Electron Back-Scatter Diffraction. The results show that various annealing temperatures and time led to a significant difference in the microstructure and texture evolution. As annealing progressed, the recrystallized volume fraction raised with the increment of annealing time, and the β-fiber rolling texture gradually developed to recrystallization texture including R, Cube and R-CubeND. Recrystallization kinetics were constructed based on the Johnson-Mehl-Avrami-Kolmogorov model. An excellent strength-ductility balance can be obtained for cryogenic-rolled samples annealed at 390°C/45 s owing to the formation of a heterogeneous structure comprising coarse grains and ultrafine grains.

Mechanism of texture evolution propelled by recrystallization behavior of interactively alternating forward extruded AZ31 magnesium alloy under pre-upsetting deformation

Pre-upsetting deformation is an effective way to optimize the microstructure of plastic forming components and achieve deep modification. In this paper, the pre-upsetting deformation of AZ31 Mg alloy billet was carried out before alternating forward extrusion, and the effect of pre-upsetting deformation temperature on the recrystallization behavior and texture evolution of AZ31 Mg alloy formed by alternating forward extrusion was analyzed. The results showed that the strains generated by the pre-upsetting deformation at different temperatures all leaded to a high dynamic recrystallization (DRX) driving force. This results in a high percentage of recrystallized grains in all pre-upsetting alternating forward extrusion (UAFE) formations. The highest percentage of recrystallized grains 94.5% was observed in U2AFE (pre-upsetting deformation at 623 K). The behavior of DRX has a significant impact on both the distribution and strength of texture. In the case of U2AFE, the maximum basal texture strength is 8.65. This is due to the maximum pole density of the deformed texture, which is composed of non-recrystallized grains and is as high as 9.25. In contrast, the maximum pole density of the recrystallized texture, which is composed of recrystallized grains, is only 8.09. Therefore, non-recrystallized grains play a crucial role in the formation of texture in UAFE. This study provides scientific guidance and technical support for the research of high-performance Mg alloy alternating forward extrusion molding technology.

Segregation-induced abnormal recrystallization behavior, texture evolution, and effects on mechanical properties in twin-roll casting 2060 Al-Cu-Li alloys

Twin-roll casting (TRC) faces persistent segregation challenges limiting widespread use., Leveraging a comprehensive suite of techniques—electron probe microanalyzer (EPMA), electron back-scattered diffraction (EBSD), and transmission electron microscope (TEM)—and rooted in a thermo-mechanical-solute integrative simulation, this study focus on a detailed exposition of the structural evolution of the 2060 Al-Cu-Li alloy, encompassing its segregation tendencies and textural transformations throughout its processing trajectory. High and low-stress TRC scenarios, TRC-3 and TRC-6, are explored. Empirical observations ascertained that the TRC venture, particularly in TRC-3, cultivates a pronounced segregation gradient, a direct offshoot of the stress gradient, thereby inducing textural disparities. During the homogenization phase, the TRC structure with diminished segregation (TRC-6) manifested signs of recovery and sustained recrystallization, an environment amiable to compositional homogeneity and tempering the pre-existing segregation. In the terminal state, a pioneering discovery elucidated that heightened segregation precipitated the β-fiber textural enhancement mechanism—a phenomenon that deteriorates properties due to the discrepancy in segregation-induced hardness. With astutely managed segregation, TRC-6 recorded tensile strengths and elongation values of 563 MPa and 7.1% respectively, marking an increment by 20.0% and 208.7% in comparison to TRC-3. This research offers vital insights into solute gradients, providing a new perspective on gradient materials.

Dynamic Recrystallization Constitutive Model and Texture Evolution of Metastable β Titanium Alloy TB8 during Thermal Deformation.

The mechanical properties of metastable β-titanium alloys are highly susceptible during the thermal mechanical processing (TMP). In this process, the recrystallization process plays an important role in determining the microstructure and texture evolution. The implementation of dynamic recrystallization (DRX), a process for achieving β-grain refinement, is considered of great significance for the improvement of the properties of metastable β-titanium alloys and their industrial production. Along these lines, in this work, an isothermal compression test of TB8 titanium alloy was carried out by using a Gleeble-3500 thermal simulator. As a result, the rheological stress behavior was analyzed, the thermal processing map was accurately established based on the stress-strain curve, and the optimal processing interval was determined. The DRX kinetic and the DRX grain size models were developed, on the basis of which a new DRX intrinsic model was established to improve the material parameters. Therefore, the actual situation in the working process could be better predicted. The microstructural evolution of TB8 titanium alloy during thermal deformation was comprehensively investigated using the electron backscatter diffraction (EBSD) technique. The obtained results demonstrate a close correlation between the diversity of DRX mechanisms in TB8 alloy and the distribution of dislocation density. Four microstructural textures during thermal deformation were identified, in which the cube texture of (001) <010> and the R-Gorss Nd texture of (110) <110> dominate. Due to the random orientation of the dynamically recrystallized grains, the strength of the R-Gorss Nd texture of (110) <110> increases with the increase in the volume fraction of DRX. On the contrary, it was verified that the dynamic recrystallization behavior has a significant weakening impact on the cube texture of (001) <010>.

Microstructural comparison of hot isostatically pressed Mo[sbnd]10Nb alloys before and after hot rolling

In this work, hot isostatic pressing (HIP) and HIP followed by hot rolling (HIP+HR) were employed to process high-performance Mo10Nb alloys, respectively. The relative density, O content, oxide types, grain size and shape, and texture type of HIP-processed Mo10Nb alloys before and after HR were systematically investigated. The results indicate that the relative densities of Mo10Nb alloys prepared by the two methods are both over 98%. The oxygen content of HIP-processed and (HIP+HR)-processed Mo10Nb alloys is 638 ± 38 ppm and 2297 ± 152 ppm, respectively. X-ray photoelectron spectrometry (XPS) confirms that the main oxides in HIP-processed Mo10Nb alloys are MoO2, MoO3, NbO and Nb2O5 while those in (HIP+HR)-processed Mo10Nb alloys are stable MoO3 and Nb2O5 resulting from the oxygen contamination during HR. More importantly, HR crushes large Nb-rich phase particles and elongates equiaxed grain in HIP-processed Mo10Nb alloys. The high temperature during HR leads to the moderate growth of grains. Noteworthy, two weak textures along {001}〈110〉 and {111}<110 > orientations were found in HIP-processed Mo10Nb alloys after HR, which could be caused by the incomplete development of deformation textures and recrystallization textures. This work helps us to clarify the microstructure difference of HIP-processed Mo10Nb alloys before and after HR, which can provide some valuable science and technology guidance for fabrication of refractory alloys by powder metallurgy and the following plastic deformation.

The origin of {113}&lt;361&gt; grains and their impact on secondary recrystallization in producing ultra-thin grain-oriented electrical steel

Abstract Ultra-thin grain-oriented electrical steel with a thickness of 80 µm is produced by one-step-rolling with industrial grain-oriented electrical steel. The research employs electron back-scattering texture analysis technique to investigate the evolution of deformation and recrystallization textures in this specific steel. Emphasis is placed on examining the origin of {113}&lt;361&gt; grains and their consequential impact on secondary recrystallization. It is revealed that primary, secondary, and tertiary recrystallization phases are integral during the annealing process. The origin of surface {113}&lt;361&gt; grains were result of initial deviated Goss grains with specific shear deformation behavior in cold rolled ultra-thin strips. Additionally, the influence of these grains on texture evolution is predominantly evident during secondary recrystallization. These grains potentially undergo abnormal growth in secondary recrystallization, exploiting high-energy grain boundaries among Goss grains. This phenomenon consequently leads to the diminution of the sharp Goss texture formed during primary recrystallization. Given the magnetic properties and predominant applications of ultra-thin grain-oriented electrical steel in medium-frequency fields, it is recommended to prepare ultra-thin grain-oriented steel during primary recrystallization phase.

Twinning-assisted static recrystallization and texture evolution in a Mg-Gd-Y-Zr alloy

The formability and mechanical properties of magnesium (Mg) alloys are strongly related to the crystallographic basal texture. Twins play critical roles in adjusting crystallographic orientation of grains during both deformation and annealing treatment via deformation twinning and twinning-assisted recrystallization. In this study, cold rolling and subsequent annealing were conducted on a Mg-5.9Gd-3.3Y-0.5Zr alloy to investigate the recrystallization behavior and texture evolution. Electron backscatter diffraction and transmission electron microscopy techniques were applied to characterize the nucleation of recrystallized grains, especially the twinning-assisted recrystallization, at multi-scales. The results indicated that a large number of {101‾2}, {101‾1} twins and {101‾1}‐{101‾2} double twins were introduced after cold rolling. The {101‾1}‐{101‾2} double twins, double twin - grain boundary intersections and dense twin-twin intersections acted as the preferential nucleation sites for recrystallization during annealing treatment, while the coarse and parallel {101‾2} twins were unfavorable for the nucleation of recrystallized grains. Although {101‾2} tension twins are the most common twins in Mg alloys, the interface of this type of twin has strong mobility and is easy to expand. Therefore, it is generally difficult for a single {101‾2} twin to recrystallize. However, the {101‾1} compression twins and {101‾1}‐{101‾2} double twins are generally difficult to expand and can store high deformation energy, so they are conducive to becoming nucleation sites for recrystallization. During the recrystallization process, the texture type (basal texture) of the cold rolled sample remained unchanged, but the overall texture intensity was significantly reduced due to the dispersion of grain orientations brought by new grains generated by twinning recrystallization.

On the role of selective nucleation and growth to recrystallization texture development in a Mg–Gd–Zn alloy

One of the main material properties altered by rare earth additions in magnesium alloys is texture, which can be specifically adjusted to enhance ductility and formability. The current study aims at illuminating the texture selection process in a Mg–0.073at%Gd–0.165at%Zn alloy by investigating recrystallization nucleation and early nucleus growth during static recrystallization. An as-cast sample of the investigated alloy was deformed in uniaxial compression at 200 °C till 40% strain and was then cut into two halves for subsequent microstructure characterization via ex situ and quasi in situ EBSD investigations. In order to gain insights into the evolution of texture during recrystallization, the contributions from dynamic and static recrystallization were initially separated and the origin of the non-basal orientation of recrystallization nuclei was traced back to several potential nucleation sites within the deformed matrix. Considering the significant role of double-twin band recrystallization in determining the recrystallization texture, this type of recrystallization nucleation was further investigated via quasi-in situ EBSD on a deformed sample, annealed at 400 °C for different annealing times. With progressive annealing, a noticeable trend was observed, in which the basal nuclei gradually diminished and eventually vanished from the annealed microstructure. In contrast, the off-basal nuclei exhibited continuous growth, ultimately becoming the dominant contributors to the recrystallization texture. The study therefore emphasizes the importance of particular nucleation sites that generate favorably oriented off-basal nuclei, which over the course of recrystallization outcompete the neighboring basal-oriented nuclei in terms of growth and thereby dominate the recrystallization texture.

Discontinuous dynamic recrystallization behavior and texture evolution of large-size pure titanium flat ingot via electron beam cold hearth melting during short process direct hot rolling

Large-size pure titanium ingots melted by single electron beam cold hearth melting (EBCHM)) could be rolled into large-width and heavy-weight titanium strip coils using short process without forging. It is crucial to study the large-span refinement mechanism from highly coarse grains, whose sizes are in the order of ∼cm, to micronmeter. In this study, the recrystallization mechanism and texture evolution of pure titanium with a size of 1570 × 200 × > 8000 mm was investigated by multi-pass simulated rolling and experimental rolling. The results indicated the hot deformation can result in marked reduction in grain size of the as-cast grain, from 3 to 5 cm to 17–23 μm. The discontinuous dynamic recrystallization (DDRX) mechanism of a pure titanium ingot during direct multi-pass hot deformation causes the reconstruction of as-cast microstructure and refinement of hot rolling microstructure. Furthermore, DDRX occurred, during hot deformation, and was accompanied with weakening of deformation texture. Raising the initial hot deformation temperature results in a modification of the texture type of the {0001} crystal plane. The strength of the texture experiences a decrease initially and then eventually an increase. This alteration in strength is inversely related to the degree of dynamic recrystallization. Based on the simulated rolling experiment, the results of experimental rolling also found the coarse as-cast grains was broken and reconstructed. It has strength (average yield strength: 334 MPa, ultimate tensile strength: 371 MPa), ductility (total elongation: 30 %). Such a combination of mechanical properties makes the hot rolling plate a potential choice for sheet practical application.

Evolution of recrystallization texture in medium to low stacking fault energy alloys: Experiments and simulations

The present work aims to investigate the evolution of static recrystallization microstructure and texture in medium to low stacking fault energy (SFE) alloys. In these categories of materials, the process of recrystallization becomes complex because of the presence of extensive deformation heterogeneity. Ni-xCo (40 and 60wt.% Co) alloy has been chosen for this purpose, where Ni-40Co belongs to medium SFE, and Ni-60Co belongs to low SFE regimes. The effect of solid solution strengthening and deformed microstructural features on the mechanism of recrystallization are explored. Both the alloys were subjected to 50% cold-rolling reduction followed by isothermal annealing at 600°C. Recrystallization texture of Ni-40Co shows a non-uniform α-fiber having a peak intensity at the Goss component, whereas Ni-60Co shows uniform α-fiber texture. Both the alloys also show rotated cube (Rt C) and rotated Cu (Rt Cu) components after recrystallization. Apart from that Ni-60Co exhibits brass recrystallization (BR) texture component. The differences in the recrystallization texture in both the Ni-Co alloys are attributed to the role of different heterogeneous deformation features in the microstructure and transition from Cu-type to Bs-type as-deformed texture. The recrystallization microstructure is dominated by the formation of substantial annealing twin (Σ3) boundaries, which also produces many new orientations; thereby weaken the recrystallization texture. These experimental findings and the proposed mechanism were used as input to simulate the recrystallization microstructure and texture in the alloy using the parallelized cellular automata (CA) technique. Parallelized CA model has successfully predicted the evolution of recrystallization texture and microstructure through simulation except parallel annealing twin feature.

Field fluctuations viscoplastic self-consistent crystal plasticity: Applications to predicting texture evolution during deformation and recrystallization of cubic polycrystalline metals

Recent advances pertaining to modeling of grain fragmentation during deformation and recrystallization of polycrystalline metals using viscoplastic self-consistent (VPSC) polycrystal plasticity are combined into a field fluctuations VPSC (FF-VPSC) model. The FF-VPSC model is a higher-order formulation calculating the second moments of lattice rotation rates based on the second moments of stress fields inside grains and resulting intragranular misorientation distributions. The misorientation distributions are used to define a grain fragmentation sub-model for improving predictions of deformation texture evolution and to formulate kinetics sub-models for nucleation as well as to influence the stored energy governing grain growth for the predictions of recrystallization texture evolution. Formation of a copper-like texture in moderately high stacking fault energy (SFE) Cu and a brass-like texture in low SFE brass during rolling to very large strains are successfully predicted using the model. Remarkably, the model also predicts recrystallization textures from the deformation textures of the two metals after adjusting tradeoffs between transition-bands and grain boundary nucleation mechanisms. Additionally, rolling and recrystallization of an interstitial-free steel, tension and recrystallization of AA5182-O, and recrystallization of an additively manufacturing cobalt-based alloy MarM-509 are simulated to predict texture evolution. Through these case studies involving multiple alloys and thermo-mechanical processes we show that, in addition to being predictive with good accuracy, the key advantage of the model lies in its versatility. The FF-VPSC model, simulation results, and insights from the results are presented and discussed in this paper.

Correlation between formability, ridging and recrystallization texture development in ferritic stainless steel fabricated by introducing intermediate annealing during cold rolling

Introducing intermediate annealing (IA) during cold rolling is a most promising approach for reinforcing ridging resistance and r-value of ferritic stainless steels, but it usually deteriorates anisotropy of r-value. To solve this problem, the texture evolution, especially recrystallization texture formation at various IA temperatures and its effect on formability and ridging was investigated. During cold rolling, the crystallite appeared along shear band because of the sequential starting of multislip systems, and due to high rotation tendency of shear component {110}〈001〉 towards stable {111}〈112〉 it owned sharp {111}<112 > and {110}<001 > components, and then during annealing, it preferentially induced recrystallized nuclei, and the γ-fiber recrystallization texture having peak intensity near {111}<112 > was formed owing to high grow tendency of preferentially formed {111}<112 > recrystallized grain. Moreover, IA at 850 °C promoted the rotation of crystallites towards stable {111}<112 > during cold rolling before final annealing compared with IA at 950 °C and above, while for IA at 950 °C and above, higher IA temperature was conducive to nucleating randomly oriented grain, and adverse to consuming other deformed grain by {111}<112 > recrystallized grains during final annealing. Therefore, the γ-fiber recrystallization texture in the final sheet gradually weakened and {110}<001 > component first strengthened and then weakened with increasing IA temperature. In addition, the banded grain clusters having similar r-value or those having same orientation and its variants with same sign of ε23 were less distinct and their size was finer in the final sheet after IA at 950 °C than those after other IA temperatures by reason of the occurrence of partial recrystallization at lower temperature and significant grain growth at higher temperature during IA. With increasing IA temperature, average r-value increasingly reduced, while anisotropy of r-value and ridging resistance first heightened and then lowered, which were lower at 850 °C and the optimal matching was realized at IA temperature of 850 °C.

Effect of extrusion parameters on microstructure and mechanical properties of Mg–6Zn–1Mn–0.2Gd alloy

The microstructure, dynamic recrystallization behavior and texture evolution of an as-extruded Mg–6Zn–1Mn–0.2Gd (ZMG610) alloy at different extrusion conditions (extrusion ratios of 25 and 45, temperatures of 350 and 400°C) were investigated. The as-cast ZMG610 alloy was mainly composed of the α-magnesium (α-Mg) matrix, the Mg7Zn3 phase and Mg3Zn6Gd (I phase). A large number of I-phase particles remained in the matrix after homogenization treatment at 330°C up to 24 h. The as-extruded ZMG610 alloy exhibited a bimodal structure consisting of fine dynamically recrystallized grains with a wide orientation spread and coarse undynamically recrystallized grains with a strong basal texture. All as-extruded samples exhibited a typical basal texture with the basal plane of most grains parallel to the extrusion direction. A lower texture intensity could be obtained by increasing both the extrusion ratio and temperature. Optimal mechanical properties (yield strength of 267 MPa, ultimate tensile strength of 360 MPa and elongation of 14.2%) were obtained through the combination of a low temperature (350°C) and a high extrusion ratio (45). Amelioration of mechanical properties highly depended on the synergistic effect of dynamically recrystallized grains, I-phase particles and texture.

Evolution of Recrystallization Texture in A286 Iron-Based Superalloy Thin Plates Rolled via Various Routes

The A286 iron-based superalloy has wide-ranging applications in replacing expensive nickel-based and cobalt-based superalloy to manufacture the turbine disk as well as the pipelines and valves of the fourth-generation supercritical water reactor (SCWR) working below 650 °C. The recrystallization texture importantly affects the mechanical properties and oxidation resistance of superalloys. However, very few investigations are available on the recrystallisation texture of A286 alloy. The current work reports the texture of A286 alloy fabrication using various rolling routes, including one-stage cold rolling with the rolling rates of 83% (Route I) and 91% (Route II), and two-stage cold rolling with the rolling rate of 83% + 50% (Route III). Route III is preferentially recommended to manufacture A286 alloy thin plates due to the obviously reduced work hardening as well as the weakened recrystallization texture and anisotropy; moreover, compared with other routes, the recrystallized grain size of Route III did not significantly coarsen. We also revealed the mechanism for the effect of cold rolling textures on the final recrystallization texture and the role of the deformation twin in {110} &lt;115&gt; grain. In this study, recrystallization texture develops through two independent mechanisms related to different deformation microstructures, including the recrystallization texture inherited from deformation texture and the recrystallization texture depended on deformation twins.

Deformation behavior and microstructure evolution of TZM alloy with 1.0 wt%ZrO2 under high temperature compression

The hot deformation behavior of TZM-1.0 wt% ZrO2 alloy in the temperature range of 1000–1600 °C and strain rate range of 0.005–1 s−1 was studied by hot compression method. The constitutive equation and hot working diagram were established, and the microstructure evolution was emphatically analyzed by SEM and EBSD. The results indicate that the flow stress decreases with the increase of temperature and the decrease of strain rate, and ZrO2 particles can improve the stability of TZM alloy in rate-control during hot deformation. The constitutive equation accurately predicted the correlation coefficient as high as 0.9685, calculated the average activation energy Q = 426 kJ mol−1, and obtained the best process parameters of 1150 °C–1250 °C /0.01–0.05 s−1 under 0.7 strain. The unstable zone was mainly composed of a small number of coarse grains and a large number of fine grains. The main reason for flow instability was the disharmonious deformation between coarse and fine grains during compression. The optimum hot working zone consists of more uniform equiaxed grains. However, EBSD observed that at a strain rate of 1 s−1, the recrystallization fraction at 1600 °C was lower than 1200 °C, and the dynamic recrystallization (DRX) and texture evolution trends at 1200 °C and 1600 °C were completely different. The abnormal changes in recrystallization fraction and texture evolution at 1600 °C were due to the competition between deformed grain growth and DRX on energy storage consumption, and the effect of deformed grain growth on energy storage consumption was greater than that of DRX. At 1600 °C/1 s−1, the growth of deformed grains was dominant, exhibiting strong texture components in the [001] direction, with〈100〉fibers as the main component and the highest peak texture strength. As the strain rate decreases, DRX dominates and weakens the texture strength, resulting in a significant decrease in<100>fibers.

Effect of pre-aging on microstructure, activation energy, texture evolution of Mg–9Gd–4Y–2Zn–0.5Zr alloy during compression deformation

This paper illustrated the effects of pre-aging on the microstructure, texture evolution, and deformation behavior of Mg–9Gd–4Y–2Zn–0.5Zr alloy during hot compression. Dynamic recrystallization (DRX) behavior, texture evolution, stress-strain curve, and activation energy of the solid solution and pre-aged alloy were evaluated. The results showed that the second-phase particles of the pre-aged samples exhibit combination of two types particles structure, which is composed of coarse dynamic precipitation particles and fine nanoparticles. The combination of these two types particles showed the best grain refinement effect by accelerating the DRX process, as the coarse dynamic precipitation particles promoted DRX through the PSN mechanism and the fine granular phase pinned dislocations and inhibited grain growth. As a result, the pre-aged samples had a higher DRX grain volume fractions and smaller average grain sizes than the solid solution alloys. In addition, the pre-aged sample had higher deformation activation energy (Q = 294.8 kJ/mol) than solid solution sample (Q = 223 kJ/mol) because β-phase pin dislocations formed during deformation restrained the movement of grain boundaries. The pre-aged alloys also showed a more concentrated texture than the solid solution alloys, with the c-axis of the coarse grains distributed from the compression direction (CD) at 30° inclination to the normal direction (ND). The c-axis distribution of the coarse grains was more scattered in the solid solution alloys. A hot processing map was constructed for the pre-aged alloy and used for evaluation. The optimal deformation parameters for the pre-aged Mg–9Gd–4Y–2Zn–0.5Zr alloy were between 0.001 and 0.1 s−1 at 400 °C–480 °C. These significant observations not only provide theoretical guidance but also practical application for setting plastic forming deformation parameters in industrial production.

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.

Revealing the grain size dependent hot workability and deformation mechanisms in a Mg-Zn-Y alloy

Despite the industrial significance of grain size for enhancing mechanical properties and formability, the in-depth deformation mechanisms at elevated temperature are still unclear. To investigate the functions of grain size on hot workability and deformation mechanisms, three groups of Mg-1.2Zn-0.2Y alloy specimens with different grain sizes were hot compressed and then studied by combining constitutive model, processing map and microstructural observations. The results showed that the enhanced hot workability accompanying low deformation activation energy and small instability regime was obtained with refined grain size. During hot deformation, the decreased grain size in Mg-1.2Zn-0.2Y alloy mainly improved the plastic deformation homogeneity, especially for the weakened local straining around grain boundaries. As a result, the dynamic recrystallization nucleation and texture development at lower strain level were influenced by the initial grain size. At higher strain magnitude, the growth and coarsening of dynamic recrystallized grains would further release strain localization and improve hot workability, while the texture was less impacted. Further, unlike the primary basal slip and deformation twinning in the specimen with coarse grain at low temperature, non-basal slips of dislocations were initiated with less deformation twins in the specimens with refined grain size.