Evolution Of Crystallographic Texture Research Articles

Impact of gas flow direction on the crystallographic texture evolution in laser beam powder bed fusion

ABSTRACT This study demonstrated that the gas flow direction in the laser beam powder bed fusion (PBF-LB) significantly affects the crystallographic texture evolved in the products. The effect on texture is attributed to the difference in the melt pool depth, which depends on gas flow direction. The melt pool was shallower when the laser scanning and gas flow directions were parallel than when they were perpendicular. This phenomenon should be of particular concern when applying Scan Strategy_XY wherein the laser was scanned with a 90° rotation in each layer, which is often used in PBF-LB. The asymmetry in the melt pool depth generated by laser scanning in the x- and y-directions can lead to unintended variations in the crystallographic texture. The gas phase would interact with a part being manufactured immediately beneath the gas and affect the crystallographic feature of the product.

Deformation, dislocation evolution and the non-Schmid effect in body-centered-cubic single- and polycrystal tantalum

A physically-informed continuum crystal plasticity model is presented to elucidate deformation mechanisms, dislocation evolution and the non-Schmid effect in body-centered-cubic (bcc) tantalum widely used as a key structural material for mechanical and thermal extremes. We show the unified structural modeling framework informed by mesoscopic dislocation dynamics simulations is capable of capturing salient features of the large inelastic behavior of tantalum at quasi-static (10−3 s−1) to extreme strain rates (5000 s−1) and at low (77 K) to high temperatures (873 K) at both single- and polycrystal levels. We also present predictive capabilities of the model for microstructural evolution in the material. To this end, we investigate the effects of dislocation interactions on slip activities, instability and the non-Schmid behavior at the single crystal level. Furthermore, ex situ measurements on crystallographic texture evolution and dislocation density growth are carried out for polycrystal tantalum specimens at increasing strains. Numerical simulation results also support that the modeling framework is capable of capturing the main features of the polycrystal behavior over a wide range of strains, strain rates and temperatures. The theoretical, experimental and numerical results at both single- and polycrystal levels provide critical insight into the underlying physical pictures for micro- and macroscopic responses and their relations in this important class of refractory bcc materials undergoing large inelastic deformations.

Experiments and Crystal Plasticity Finite Element Simulations of Texture Development during Cold Rolling in a Ti-15V-3Cr-3Sn-3Al Alloy

The effect of deformation on the evolution of crystallographic texture in a Ti-15V-3Cr-3Sn-3Al (Ti-15333) alloy after unidirectional cold rolling was studied experimentally and numerically in the present investigation. An optical microscope (OM) and scanning electron microscope (SEM) were used to study the microstructures, while the crystallographic texture after cold rolling was studied with X-ray diffraction. The rolling process (deformation) was simulated with PRISMS-plasticity, open-source crystal plasticity software. Micro-indentations were performed on the initial solution-annealed sample with an equiaxed grain structure. The experimentally obtained load–displacement curve for a particular grain (orientation-φ1, Φ, φ2 = 325.2°, 18.0°, 66.2° (Bunge notation)) was compared with the crystal plasticity finite element method (FEM)-simulated load–displacement curve to obtain the calibration parameters. The obtained parameters, along with the experimental stress–strain curve, were used to recalibrate the PRISMS-plasticity software for the rolling simulations of the Ti-15333 alloy. It was observed that the γ-(normal direction, ND//<111>) and α-(rolling direction, RD//<110>) fibers strengthened with cold rolling, experimentally as well as numerically. The simulated orientation distribution functions (ODFs) matched reasonably well with those obtained from the experiments. The average values of von Mises stress and von Mises strain increased with an increase in deformation.

Microstructure-texture-micro-strain evolution during tensile deformation of α+β titanium alloy using in-situ Synchrotron X-ray diffraction and CPFEM simulation

The evolution of micro-strain and crystallographic texture of each phase of α+β Ti-6Al-4V titanium alloy generated during tensile deformation has been estimated numerically and then compared with the experimental results. It has been carried out based on the Crystal Plasticity Finite Element Model (CPFEM) simulation of the stress-strain curve till the uniform elongation for the equiaxed microstructure is generated synthetically. The synthetic microstructure of Ti-6Al-4V has been developed using the microstructure feature parameters (such as grain size, phase fraction, and grain orientation). The polycrystal stress-strain behaviour for the same has been simulated using the representative orientation distribution function data obtained from the electron backscatter diffraction (EBSD) scans. The present investigation discusses the mechanism of strain-partitioning during uniform elongation using CPFEM simulation in conjunction with EBSD-based experimental misorientation data to rationalize our observation.

Evolution of Crystallographic Texture, Microstructure, and Mechanical Properties during Flat Rolling of Alloys of the Cu–Zn System with Different Grain Sizes

Evolution of Crystallographic Texture, Microstructure, and Mechanical Properties during Flat Rolling of Alloys of the Cu–Zn System with Different Grain Sizes

Effect of Accumulative Roll Bonding (ARB) strain path on microstructural evolution and crystallographic texture development in aluminium

In the present study nine successive ARB cycles were applied on double-layer 1 mm aluminum sheets following three different routes; normal, reverse and cross. Severely deformed sheets were studied by XRD and EBSD to show the evolution of crystallographic textures, while mechanical properties are characterized by micro-tensile and micro-hardness tests. Results indicate that changing the route significantly affects the formation of crystallographic texture components in the structure, leading to different macro mechanical properties. As the asymmetry increases in the strain route, the intensity of the texture components reduces by 57% from as-received structure to the most asymmetric ARBed sample, i.e., cross route. The difference is attributed to different activated slip system in each route. The higher the asymmetry of the route, the lesser the necessity for the cross-slip, and the more the dynamic recrystallization in the structure. Hence, the finest grains happen to form in Normal ARBed sample. The same mechanism is responsible for higher strength (36%) and hardness (32%) observed in Normal ARBed sample. However, the change of route also lowers the bond strength in Cross and Reverse ARBed samples, weakening them by almost 12% regarding the as-received sheet.

Near-Net Shape Manufacture of Ultra-High Strength Maraging Steel Using Flow Forming and Inertia Friction Welding: Experimental and Microstructural Characterization

Abstract Flow forming and inertia friction welding (IFW) have been widely used as manufacturing processes that produce high-value engineering components. Combining these two advanced processes facilitates the fabrication of near-net shape components leading to optimized designs. This study introduces the joining of flow-formed seamless tubes of MLX®19 maraging steel using the IFW process to fabricate a near-net shape component used in landing gears and missile parts. The as-received material was initially provided ≈30% reduction in thickness from the flow forming trials and then welded at four varying weld energies while maintaining constant friction and forge pressures. The mechanical behavior of the weldments was characterized, and the optimized weld parameters were determined. The concomitant microstructural evolution of the optimized weld was also examined to comprehend the underlying deformation mechanisms. The weld strength, axial shortening, and width of dynamic recrystallization (DRX) displayed an increasing trend with an increase in the weld energy. The weld-zone (WZ) and thermomechanical affected zone (TMAZ) showed the presence of martensite, whereas in the HAZ presence of intermetallic precipitates and reverted austenite was confirmed along with tempered martensite. Based on microstructural evidence, it was concluded that the peak temperature attained in the WZ was above Ac3, whereas in the TMAZ it was in-between Ac1 and Ac3. The evolution of crystallographic texture implied that WZ was subjected to pure shear deformation during the welding whereas the TMAZ experienced a combined shear and compressive deformation.

Effect of Process Temperature on the Texture Evolution and Mechanical Properties of Rolled and Extruded AZ31 Flat Products

The application of magnesium flat products is affected by the limited formability at room temperature and the anisotropy of the mechanical properties. The main reason for this is the underlying hexagonal crystal structure of magnesium and the development of strong crystallographic textures during massive forming processes with distinct alignment of basal planes. For an improvement in the properties of semi-finished products, the detailed knowledge of the influence of the manufacturing process on the microstructure and texture evolution of the flat products as a result of dynamic and static recrystallization is required. In this work, flat products made of conventional magnesium alloy AZ31 were manufactured by the rolling process as well as by direct extrusion, with variation in the process temperature. This allowed the development of a distinct variation in microstructures and textures of the flat products. The effects on mechanical properties and formability are highlighted and discussed in relation to the microstructure and texture. It is shown that both the process and the temperature have a major influence on texture and consequently on the material properties.

Additive friction stir deposition of AZ31B magnesium alloy

The current work explored additive friction stir deposition of AZ31B magnesium alloy with the aid of MELD® technology. AZ31B magnesium bar stock was fed through a hollow friction stir tool rotating at constant velocity of 400 rpm and translating at linear velocity varied from 4.2 to 6.3 mm/s. A single wall consisting of five layers with each layer of 140×40×1 mm3 dimensions was deposited under each processing condition. Microstructure, phase, and crystallographic texture evolutions as a function of additive friction stir deposition parameters were studied with the aid of scanning electron microscopy including electron back scatter diffraction and X-ray diffraction. Both feed material and additively produced samples consisted of the α-Mg phase. The additively produced samples exhibited a refined grain structure compared to the feed material. The feed material appeared to have a weak basal texture, while the additively produced samples experienced a strengthening of this basal texture. The additively produced samples showed a marginally higher hardness compared to the feed material. The current work provided a pathway for solid state additive manufacturing of Mg suitable for structural applications such as automotive components and consumable biomedical implants.

Evolution of microstructure and crystallographic texture throughout the rolling process of AA3104

The metallic components are manufactured through several thermomechanical processes. Each selected procedure has multiple targets. The first target is to obtain the required dimensional criteria and second, to achieve the ideal mechanical response toward the application. This is currently accomplished through years of knowhow combined with an academic background of materials science and engineering. Since metals are polycrystalline materials, the several rotations of the crystals, the preferred orientation also known as texture, and their interactions, are crucial characteristics that are directly correlated to the final response of the material, and one could apprehend its thermomechanical prehistory as well as predict is behavior. Different atomic arrangements act differently texture-wise therefore in the current review article, the evolution of the microstructure and the crystallographic texture through the thermomechanically rolling process especially of Al alloys for packaging applications is analyzed. The crystallographic texture evolution in 3xxx Al alloys in different processing routes is presented and compared to the anisotropic effects occurring during deep drawing. The earing phenomena in Al alloys are correlated to the produced texture and therefore their understanding is crucial in order to highlight the importance of texture control throughout the thermomechanical process.

Crystallographic texture evolutions of Ti-6Al-4V chip foils in relation to strain path and high strain rate arising from large strain extrusion machining process

Large strain extrusion machining (LSEM) is a promising process to create chip foils with ultrafine grains and a certain type of crystallographic texture. Disclosing the interconnection between the deformation histories and the crystallographic texture variations resulting from the LSEM process is vital for the texture generation and control of Ti-6Al-4V chip foils. Electron-backscattered diffraction and viscoplastic self-consistent (VPSC) simulation were combined based on numerical simulation to study evolutions of crystallographic textures for chip foils during LSEM of Ti-6Al-4V. The deformation histories during LSEM process were also analyzed by coupling theoretical analysis with digital image correlation technique. The role of individual type of slip system on the texture variation of Ti-6Al-4V chip foils was identified by modifying the Voce hardening parameters in VPSC model. It is seen that strain path controlled by the chip thickness ratio changes the inclination of generated textures in chip foils. Basal and 1-st order pyramidal <c+a> slip systems are the main deformation modes in high strain rate deformation condition of LSEM process. Similar textures are formed under large strain and high strain rate deformation in LSEM comparing with that in free machining process. The conclusions are useful to control the crystallographic texture generation in LSEM of Ti-6Al-4V by optimizing cutting speeds and chip thickness ratios.

Coupling crystal plasticity and cellular automaton models to study meta-dynamic recrystallization during hot rolling at high strain rates

Predicting microstructure and (micro-)texture evolution during thermo-mechanical processing requires the combined simulation of plastic deformation and recrystallization. Here, a simulation approach based on the coupling of a full-field dislocation density based crystal plasticity model and a cellular automaton model is presented. A regridding/remeshing procedure is used to transfer data between the deformed mesh of the large-strain crystal plasticity model and the regular grid of the cellular automaton. Moreover, a physics based nucleation criterion has been developed based on dislocation density difference and changes in orientation due to deformation. The developed framework is used to study meta-dynamic recrystallization during double-hit compression tests and multi-stand rolling in high-resolution representative volume elements. These simulations reveal a good agreement with experimental results in terms of texture evolution, mechanical behaviour and growth kinetics, while enabling insights regarding the effect of nucleation on kinetics and crystallographic texture evolution.

シリサイドを例にした金属積層造形法による集合組織発達の支配因子解明

シリサイドを例にした金属積層造形法による集合組織発達の支配因子解明

Hot isostatic pressing of laser powder-bed-fused 304L stainless steel under different temperatures

Hot isostatic pressing (HIP) is becoming a key strategic technology for post-processing metallic materials fabricated with laser powder bed fusion (LPBF), acting to eliminate the processing-induced pores and improve the mechanical properties. This paper comprehensively investigated material characteristics (porosity, residual stress, microstructures, phase composition, and inclusion), mechanical properties (microhardness, tensile properties, and fatigue properties), and deformation behaviors of LPBF 304L austenitic stainless steel (ASS) subjected to HIP process with different temperatures (965°C, 1165°C, and 1365°C). Experimental results indicated that the grain size, inclusion size, recrystallization fraction, and dimple size increased with increasing HIP temperature, which resulted in homogenized microstructure, reduced yield strength and microhardness, and significantly improved ductility. The fatigue life of HIP-treated samples after surface post-treatment was mainly influenced by porosity, inclusion, residual stress, and dislocation density. The HIP-1165°C samples with low porosity and small-sized inclusions had a higher fatigue life than HIP-965°C and HIP-1365°C samples. In addition, the evolution of crystallographic texture and inclusion composition associated with the HIP temperature were systematically revealed with the aid of orientation distribution function (ODFs) and elemental mappings. This study provides a profound understanding of the rational design of the hybrid process of LPBF and HIP.

Unveiling the room-temperature softening phenomenon and texture evolution in room-temperature- and cryogenic-rolled ETP copper

The present study addresses the evolution of microstructural and crystallographic texture in room-temperature-rolled (RTR) and cryogenic-rolled (CR) electrolytic tough-pitch (ETP) copper. Copper specimens were subjected to 20, 40, 60, and 80% reductions via RTR and CR processing. The microstructure evolution of the severely deformed RTR and CR specimens revealed deformed and recrystallized grains. Static recrystallization (SRX) at room temperature (RT) was observed in the severely deformed RTR and CR specimens. Both discontinuous SRX (DSRX) and continuous SRX (CSRX) were responsible for the nucleation of small grains at RT. Particle-stimulated nucleation (PSN) was also responsible for small-grain formations around the Cu2O particles. The initial ETP copper specimen showed a weak texture whose intensity increased after the RTR and CR deformation. The texture intensity of the severely deformed specimens was affected by both deformation and the SRX phenomena. The CR specimens showed texture that was stronger than that of the RTR specimens up to the point of an intermediate reduction (60%), whereas at higher deformation (80%), the RTR specimens showed stronger texture intensity compared with that of the CR specimens. The texture weakening in the CR80 specimen was due to the formation of strain localizations (SLs) and to the nucleation at SLs. Large amounts of stored energy and SL formation in severely deformed CR specimens led to a different recrystallization texture compared with that of RTR specimens. A Cube component was dominant in the RTR80, whereas Goss, Copper and S components were observed in the CR80 specimen for SRX grains. The CR specimen showed a relatively high hardness value compared with the RTR specimen. Time-dependent decay in the hardness values for both the RTR and the CR specimens were attributed to room-temperature recovery (SRV) and recrystallization (SRX).

Study of the evolution of crystallographic texture during the drawing of a low-alloyed aluminum alloy

The problem of the crystallographic texture evolution in the process of cold stamping of aluminum alloys is considered on the example of the drawing process. For the study, an X-ray diffraction texture analysis of a cold-rolled strip made of a low-alloy aluminum alloy 8011 was carried out. Then, two caps were stamped from the strip with different degrees of deformation, for which the texture composition was also determined. The drawing process of both caps was calculated in the Ansys-LS-Dyna software package in order to establish the stress-strain state. On the basis of these calculations, further modeling of the rotation of texture components characteristic of aluminum after cold deformation was carried out in the TEXT_LATENT_HRD software product. Experimental data showed significant differences in the texture composition of cold-rolled strip and caps. After cold rolling, three typical textures of brass (Bs), S, and Cu, characteristic of the deformed state, are noted; these orientations are manifested with almost the same intensity. At the same time, after drawing, a Goss texture is observed, which is especially pronounced in a high cap; the bs texture practically disappears, and the &beta; textures rotate towards the S orientation. Modeling shows that the components have different stability during the drawing process, for example, Goss and S textures practically do not change their intensity. In this case, the Bs-texture is unstable, the orientations in the space of Euler angles begin to shift from it to the Goss-texture. Such a change differs from that observed during cold rolling in that, as a result of the rotation of the crystal lattice, the material with the Bs orientation acquires the S orientation. Differences in the evolution of texture components during drawing and cold rolling are explained by the difference in the normalized velocity gradients, which has a different effect on the rotation of the crystal lattice at equal plastic deformation by sliding for different crystallographic orientations.The study was supported by a grant from the Russian Science Foundation,&nbsp;project 18-79-10099-P, https://rscf.ru/project/21-79-03041/.

Quasi-in-situ study on the crystallographic lattice rotation of tantalum during compression deformation

By employing a quasi-in-situ method, we investigated the crystallographic texture evolution process of high purity tantalum during compression deformation. The influence of grain size, aspect ratio, and initial orientations on the crystallographic lattice rotation process was analyzed in-depth using the electron backscatter diffraction technique. It is found that the randomly distributed grain orientations mainly evolve toward {111} and {100} orientations during compression, forming the two typical deformation textures in body-centered cubic metals. Furthermore, the crystallographic rotation direction and degree have no apparent linear relationship with grain size or grain aspect ratio but are mainly related to the grain orientation. Especially, the slight crystallographic rotation angle for {100} grain is primarily associated with the activation of multiple slip systems. Multiple slip systems mean different slip planes and different slip directions, and it is difficult for {100} grains to be dominated by a certain slip system and rotate to a large extent like {111} grains. In comparison, the large crystallographic rotation angle for {110} grain is mainly related to the strain coordination in local regions. {110} grains are easier to active slip systems than grains with other crystal plane orientations inferred from the critical shear stress, thereby the rotation of grains and inhomogeneous deformation occurred during the compression process.

Annealing texture in asymmetrically rolled Ni1.5FeCrCu0.5 high-entropy alloy

Asymmetrical cold rolling (ACR) was conducted on Ni1.5FeCrCu0.5 high-entropy alloy (HEA) with various velocity ratios (VRs) between the top and bottom rolls from one to eight. The crystallographic texture evolution in the annealed samples was investigated using the X-ray diffraction (XRD) method. Macro texture measurements revealed that the asymmetrical cold rolling increased the intensity of shear texture components such as E {111} <110> and F {111} <112> orientations. It was found that recrystallization was unfavorably suppressed by the low stacking fault energy (SFE) of the alloy. The results indicated that increasing the VR of the rolls led to the formation of Goss {011} <100> and Goss/Brass {011} <115> orientations in the annealed HEAs. Moreover, the Cube {001} <100> component in the homogenized sample disappeared by the post-roll annealing. However, the intensity of Brass {011} <211> orientation almost remained unchanged (⁓3 × R) in the annealed samples. Our findings showed that the increase in the VR of the rolls gave rise to a continuous rotation of 25° from the S {123} <634> orientation towards the Brass {011} <211> component in the annealed HEAs. Finally, plastic anisotropy measurements revealed that the drawability of the annealed sheets was continuously improved by increasing the VR of the rolls.

Evolution of microstructure and crystallographic texture during cold rolling of liquid phase sintered tungsten heavy alloy

In this study, the evolution of microstructure and crystallographic texture of two-phase tungsten heavy alloy (almost pure tungsten embedded in nickel‑tungsten‑iron matrix) during cold rolling was investigated systematically. Electron back scatter diffraction studies reflected that the matrix phase accommodates more strain in the early stages of deformation and that as deformation progresses, the matrix phase exhausts its work hardening ability, resulting in the onset of micro-shear band formation. The tungsten phase on the other hand showed the presence of large orientation gradients accompanied with significant flattening and elongation of grains. At higher rolling reductions (effective true strain of −2.66), extensive shear bands spanning across several tungsten particles and the matrix were observed in the microstructure, which in turn had implications on the evolution of the crystallographic texture. It was observed that weak αb. c. c. (<110>∥RD) and γ fiber (<111>∥ND) emerge in tungsten at low to intermediate rolling reductions, and that αb. c. c. fiber strengthens much more than γ fiber at higher rolling reductions with prominent intensity at rotated cube position. For the matrix phase, a weak beta fiber (fiber connecting the brass {011}<211>, copper {112}<111>, and S {123}<634> orientations in the Euler space) was observed at low to intermediate rolling reductions, followed by strengthening of Goss and Brass orientations at higher rolling reductions.

Microstructure and Crystallographic Texture Evolution during Isothermal Annealing of Cold-Rolled Fe-6.8Al Low-Density Steel

In the present work, the microstructural evolution in heavily cold-rolled and annealed Fe-6.8Al low-density steel has been studied. The evolution of texture with a strong component \(\left\{ {001} \right\}\langle 110\rangle\) has been observed upon cold rolling. After recrystallisation, the formation of texture with \(\left\{ {111} \right\}110\) component and other γ fiber orientations with weak intensities have been noticed. The mechanism of recrystallisation is discontinuous recrystallisation. The evolution of texture with near \(\left( {04\overline{1}} \right)\left[ {501} \right]\) and \(\left( {31\overline{8}} \right)\left[ {\overline{4}\overline{3}\overline{2}} \right]\) components in the partially recrystallised microstructures have been observed. The recrystallised grains nucleate close to the boundaries of the deformed grains and are bounded by high angle grain boundaries which are easily identified from the image quality maps. Analysis of grain size of the annealed samples shows that the presence of Al reduces the grain boundary mobility by solute drag.