Strong Recrystallization Texture Research Articles

Effects of Zr and Hf on superelasticity, shape memory effect and microstructure of β-type (Ti–Zr–Hf)–Nb–Sn multi-principal element alloys with low magnetic susceptibility

(Ti–Zr–Hf)(97−x)–xNb–3Sn (Ti:(Zr + Hf) = 1:1) alloys were designed for biomedical superelastic alloys with magnetic resonance imaging (MRI) compatibility. The effects of Zr and Hf on constituent phases, superelasticity, shape memory effect and magnetic susceptibility were clarified. The specific Nb content for superelasticity and shape memory effect was also explored. It was found that the (Ti–Zr)–6.5Nb–3Sn alloy exhibited a superelastic recovery strain of 5.2 % with lower magnetic susceptibility compared to conventional Ti–Ni and Ti–Nb alloys. The magnetic susceptibility decreased with increasing Hf content. The (Ti–Hf)–9Nb–3Sn alloy showed a superelastic recovery strain of 0.9 % and very low magnetic susceptibility less than half of that of the conventional alloys. Based on the lattice parameters of these alloys, it was found that these alloys exhibited larger transformation lattice strain between a β phase and an α” phase than those of the Ti–Nb alloys, suggesting high potential to exhibit a large superelastic recovery strain. According to orientation analyses of constituting grains, the larger superelastic recovery strain in the (Ti–Zr)–6.5Nb–3Sn alloy than that of the (Ti–Hf)–9Nb–3Sn alloy is considered to be caused by a strong recrystallization texture of {001}β <110>β. By optimization of heat-treatment temperature, superelastic recovery strain of 3.6 % was achieved in the (Ti–0.5Zr–0.5Hf)–7.5Nb–3Sn alloy.

The evolution of microstructure and texture induced by grinding and subsequent thermal exposure of single crystal alloy

The dynamic recrystallization (DRX) behavior during grinding and static recrystallization (SRX) behavior during thermal exposure of Ni-based single crystal alloy were compared in this work. The microstructure changes after DRX and SRX were characterized by field emission scanning electron microscopy (FE-SEM) and scanning transmission electron microscopy (STEM). The grain orientation and dislocation density distribution were analyzed by transmission Kikuchi diffraction (TKD) and electron backscatter diffraction (EBSD). The results show that SRX is affected by DRX process on the ground subsurface of single crystal alloy. The nucleation sites of SRX at high temperature are derived from significant number of high-density dislocation structures generated by DRX that induced by grinding process. Compared with the equiaxed nanograins produced by DRX, micron-scale cellular and equiaxed grains are formed on the surface, and dislocation density decreases sharply after SRX. The original cube texture of single crystal superalloy changes into shear texture due to plastic deformation during grinding, and then into strong recrystallization texture at high temperature. The microstructure changes under deformation and high temperature directly affect the final properties of single crystal blades. It is of great practical significance to understand the microstructure evolution and grain orientation changes during DRX and SRX processes, so as to reveal the mechanism of single crystal transforming into polycrystal from machining process to service stage of single crystal blades.

Gradient Recrystallization Behavior of a Moderate Warm-Rolled Non-Oriented Fe-6.5wt%Si Alloy

In Fe-Si alloy systems, the Fe-6.5wt%Si alloy shows low iron core losses and near-zero magnetostriction, thus having great potential for high-frequency applications. In this study, an Fe-6.5wt%Si alloy hot band was subjected to a moderate warm rolling with a thickness reduction of 40%, and then annealed at different temperatures. The recrystallization behavior was investigated using the EBSD technique. After the moderate warm rolling, the initial gradient structure of the hot band is inherited, leading to gradient recrystallization behaviors during the further annealing process. The sheet surface first densely nucleates and forms strong &lt;110&gt;//ND and {221}&lt;114&gt; textures. However, the &lt;110&gt;//ND and {221}&lt;114&gt; grains have fewer high-mobility and high-energy (20–45°) boundaries than the other oriented matrix grains, leading to insufficient growth advantages. In the center region, the recrystallization is slow, but the nuclei usually have larger sizes. The inheritance of the &lt;001&gt;//ND (θ-fiber) texture from the initial hot band appears. Some θ-fiber grains, which have easy-magnetized &lt;001&gt; axes lying in the sheet plane, preferentially nucleate in the strong α-fiber textured matrices and form a strong θ-fiber recrystallization texture in the center region.

Investigation of tensile properties and microstructural evolution of Al–Mg–Si alloy produced through the multi-axial forging at −147 C and room temperature

In current investigation, effect of Multi-axial forging (MAF) processing temperature on microstructural evolution and mechanical properties of Al–Mg–Si alloy was investigated by performing MAF at (i) −147 °C (CT-MAF) and (ii) room temperature (RT-MAF). The electron Back scattered diffraction (EBSD) and transmission electron microscopy (TEM) were used for exploring the microstructural evolved. It was observed that MAF at −147 °C helped in accumulation of large amount of dislocations as confirmed from the TEM. The recovered, recrystallized, sub-grain and deformed grains were separated with the help of EBSD, using criteria based on grains orientation spread (GOS) and grain tolerance angle, and further correlated with the mechanical properties. The strong recrystallization texture (Goss texture ({110} <001>), and rotated Goss texture ({110} <110>)) were observed in CT-MAF sample as compared to RT-MAF sample. The average ultimate tensile strength and average hardness increased after the CT-MAF to 370 MPa and 124 VHN, respectively, almost average ultimate tensile strength (UTS) increased by 23% and average hardness increased by 33% as compared to RT-MAF sample. It was observed that at −147 °C processing temperature strain hardening mechanism was dominated in CT-MAF sample, whereas due to the room temperature processing temperature softening mechanism was dominated in RT-MAF sample.

Microstructure and unusually strong recrystallization texture of the FCC phase of a cost-effective high-strength dual-phase AlCrFe2Ni2 high entropy alloy

The evolution of microstructure and recrystallization texture was investigated in a severely deformed (90% cold-rolled) and annealed (FCC + BCC/B2) AlCrFe2Ni2 high entropy alloy (HEA) with an exclusive focus on the FCC phase. Cold-rolling resulted in pronounced bending and folding of the lamellae, progressive alignment of the phases along the RD, large misorientation gradient in the FCC phase, and finally ultrafine structure formation. The FCC phase showed a predominantly brass-type (B) texture with orientations spreading from the G ({011}<100>) to B ({011}<112>), indicating its low stacking fault energy (SFE). The prior cold-rolling deformation strongly influenced the annealing behavior, including lamellar to microduplex structure, grain boundary character evolution, and faster attainment of equilibrium phase fractions. The 90% cold-rolled and annealed material revealed the presence of a remarkably strong B component, unlike the weak recrystallization texture of typical FCC single-phase low SFE HEAs. The origin of the strong B recrystallization component was attributed to a combined effect of the high misorientation gradient in the FCC phase, increased boundary mobility at high annealing temperatures, and the presence of the BCC/B2 phase inhibiting grain growth and thus preserving the recrystallized B grains. The tensile properties of the HEA were evaluated to highlight the outstanding cost-performance advantage of the alloy.

Dependence of recrystallization behavior and magnetic properties on grain size prior to cold rolling in high silicon non-oriented electrical steel

The present work aimed to investigate the roles of prior grain size of the hot rolled sheets after normalization on final recrystallization behavior and magnetic properties in 3.1%Si + 0.9%Al non-oriented electrical steel. Bigger prior grain size produced coarser deformed grains and promoted the development of in-grain shear bands, which together resulted in distinct recrystallization behavior. The prior small-grained microstructure caused relatively slow kinetics at the early stage of recrystallization, while fast kinetics was displayed at the later stage due to the growth of new γ(<111>//normal direction (ND))-grains and led to strong γ-fiber recrystallization texture. By contrast, the prior big-grained microstructure gave rise to relatively fast recrystallization kinetics at the early stage due to the diversified nucleation orientation and rapid grain growth in the interior of coarse deformed γ-grains with the help of in-grain shear bands. However, relatively slow kinetics was displayed at the later stage because the coarse deformed λ(<001>//ND)-grains were sluggish to recrystallize. Hence, continuous recrystallization and shear bands induced nucleation contributed to strong λ-fiber texture. Magnetic induction B50 continuously improved as the prior grain size increased, while both the low-frequency core loss P15/50 and the high-frequency core loss P10/400 decreased firstly and then increased with different critical prior grain size.

η-fiber microstructure and texture evolutions in ultra-thin silicon steel

0.08mm ultra-thin silicon steel is prepared with 0.30mm commercial grain-oriented silicon steel as raw material, and the evolutions of η-fiber microstructure and texture are investigated with emphasis. During rolling deformation, initial Goss orientation shows crystal rotation to {111 }<112> orientation. With the increase of rolling reduction, the retention of Goss orientation is reduced and more observed near the sheet surface. For initial deviated Goss oriented grains, {111}<112> and η-fiber oriented areas are also observed in 0.08mm rolled sheet, while the accuracy and concentration of these two components are decreased. During annealing, η-fiber nucleation superiority in γ-fiber deformed regions is significant, and thus contributes to strong η-fiber recrystallization texture. When the rolled sheets are heated at 800 °C for 15 min, strong η-fiber recrystallization texture and uniform microstructure is beneficial for the magnetic properties of ultrathin silicon steel sheets.

Microstructure evolution and mechanical properties of double-sided friction stir welding between AA6061-T6 and AA7075-T651

The present study appraises the effect of tool rotation direction during dissimilar double-sided friction stir welding of AA6061–AA7075 thick plates. The mechanical strength, fracture behavior and the microstructure evolution for the joints are studied. Sound joints without defect and higher strength was achieved for the joint wherein tool rotation in the second weld is provided in the reverse to that of the first weld. Electron backscatter diffraction of welded joints revealed finer grains at the weld center than observed below the tool shoulder affiliated to high degree of deformation/strain. Pole figures revealed the dominance of high shear texture B/B¯ and C components at the weld center. Orientation distribution function revealed the presence of strong intensity recrystallization texture components Cube {001}<100>, Goss {110}<001> and P {011}<112> at the weld center.

Evolution of Annealing Twins and Recrystallization Texture in Thin-Walled Copper Tube During Heat Treatment

Thin-walled copper tubes are usually produced by multi-pass float-plug drawing deformation. In general, the annealing treatment subsequently is necessary to release the stored energy and adjusts the microstructure. In this study, an investigation on the evolution of annealing twins as well as textures in the thin-walled (Ф6 mm × 0.3 mm) copper tube underwent holding time-free heat treatment was reported. Electron backscattered diffraction analysis reveals that a large number of Σ3 boundaries (60° 〈111〉 twin relationship) are produced at the early stage of heat treatment, which is due to the lower boundary energy. With the recrystallization proceeding, the migration rate of grain boundaries decreases on account of the grain growth; meanwhile, the unique Σ9 boundaries (38.9° 〈110〉 relationship) are formed due to the interaction of the Σ3 boundaries. As a result, the number fractions of Σ3 boundaries and high-angle grain boundaries decrease rapidly. During the grain growth stage, a strong recrystallization texture was formed due to the fact that the grains of Goss orientation have a growth advantage over the others. As a result, the initial copper texture was transferred into the Goss texture in domination.

Superelasticity and tensile strength of Ti-Zr-Nb-Sn alloys with high Zr content for biomedical applications

In this study, Ti-xZr-8Nb-2Sn (x = 40, 45, 50) (at.%) alloys were fabricated by arc melting method and then microstructures, martensitic transformation behavior, superelasticity and mechanical properties were investigated by means of optical m icroscopy, electron microscopy, X-ray diffraction, tensile test and Vickers hardness test. The alloys consisted of β phase only at room temperature and exhibited strong (200)β texture after solution treated at 1173 K for 1.8 ks. Athermal ω phase was not observed from transmission electron microscopy in the alloys. The stress induced β→α″ transformation and the reverse transformation occurred on loading and unloading, respectively. Transformation temperature (Ms(C-C)) decreased from 188 K to 77 K with increasing Zr content from 40 at.% to 50 at.%. The maximum recoverable strains for 40Zr, 45Zr and 50Zr alloys were 7.1%, 7.5% and 7.3%, respectively, which was due to a combined effect of the large lattice deformation and a strong recrystallization texture. All alloys were fractured in ductile manner with fracture strains larger than 25%. Ultimate tensile strength of 835 MPa and superelastic recovery strain of 5.5% were obtained at room temperature in the solution treated Ti-40Zr-8Nb-2Sn alloy.

Effect of normalization on texture evolution of 0.2-mm-thick thin-gauge non-oriented electrical steels with strong η-fiber textures

Thin-gauge non-oriented electrical steel sheets of 0.2 mm in thickness with high magnetic induction and low core loss were produced by a two-stage cold-rolling method with and without normalization annealing. The through-process texture evolutions of the two processes were compared and studied by means of X-ray diffractometer and electron backscattered diffraction. Results showed that excellent magnetic properties were attributed to strong η-fiber recrystallization texture in the final sheet. Coarse γ-fiber-oriented grains after intermediate annealing and medium cold-rolling reduction were considered key factors to obtain a strong η-fiber texture given that a large number of shear bands within the γ-fiber deformed matrix provided dominant nucleation sites for η-fiber-oriented grains. The normalization annealing after hot rolling was favorable for the retention of cube texture, thereby decreasing the magnetic anisotropy of thin-gauge non-oriented electrical steels.

Enhancement of recrystallization texture in non-equiatomic Fe-Ni-Co-Al-based high entropy alloys by combination of annealing and Cr addition

Formation of strong <001> recrystallization texture in new non-equiatomic Fe-Ni-Co-Al-based high entropy alloys has been investigated. Optimal annealing temperature and time to obtain strong <001> texture is subsequently determined through microstructure and recrystallization texture study of cold-rolled NCACB (34.95Fe-27.5Ni-17.5Co-11.5Al-8.5Cr-0.05B at.%) at 1200 °C and 1300 °C for different annealing times. It has also been found that the recrystallization texture is influenced by grain growth and the relative grain size (d/t, d-grain size, t-sheet thickness). Furthermore, contribution of chemical composition to <001> texture has been examined in two additional cold-rolled non-equiatomic high entropy alloys, NCAB (Fe-27.5Ni-17.5Co-11.5Al-0.05B at.%) and NCATB (Fe-27.5Ni-17.5Co-11.5Al-2.5Ta-0.05B at.%), under the same optimal annealing condition used for NCACB. Comparison of texture intensity of NCAB, NCATB, and NCACB demonstrates that Cr is very effective in the formation of strong <001> recrystallization texture of Fe-Ni-Co-Al-based alloys. Based on low-angle boundary statistics, it is hypothesized that decrease in stacking fault energy is responsible for the enhanced recrystallization texture in NCACB. Additionally, it is demonstrated employing a Zener-type model for the pinning of grain boundaries by second-phase particles, that precipitated NiAl particles facilitate the abnormal grain growth in NCACB. The tensile tests results show that strong recrystallization texture and bamboo-like structure improve the ductility of NCACB.

Effect of Al addition on superelastic properties of Ti–Zr–Nb-based alloys

The effects of Al addition on the superelastic properties of Ti–Zr–Nb alloys were investigated. Ti–18Zr–(12–16)Nb–(0–4)Al (at.%) alloys were prepared by the Ar arc melting method and superelastic properties, transformation temperature, and transformation strain were investigated quantitatively. The superelastic strain increased by the addition of Al and a large recovery strain of 6.1% was observed in a Ti–18Zr–13.5Nb–3Al alloy. The large superelastic strain of Al-added alloys was found to be due to a large transformation strain and a strong recrystallization texture.

Microstructure and superelasticity of a biomedical β-type titanium alloy under various processing routes

The influences of various processing routes including cold forging, suction casting, cold rolling, hot compression and hot forging on the microstructure, mechanical properties and superelasticity of Ti-7.5Nb-4Mo-2Sn alloy were investigated. It has been found that, the alloy processed by cold rolling, hot forging, cold forging and suction casting contained a single β phase, but the alloy after hot compression consisted of a duplex structure of α and β phases. The alloy exhibited an average grain size of about 4μm after suction casting processing, indicating excellent grain refining effect. A strong recrystallization texture {111}〈110〉 was well developed in the cold rolled and hot forged alloys; while cold forged and hot compressed alloys exhibited strong multiple textures in different directions associated with their deformation. Superelastic behavior was observed in the cold rolled, suction casted, hot forged and hot compressed alloys, in which the casted alloy exhibited the highest strain recovery rate which reached nearly 75%, and the hot compressed alloy showed higher stress for inducing martensitic transformation but lower recovery rate due to the complex multiple textures formed during hot compressing processing among the alloys after different processing routes.

Development of Cube Recrystallization Texture in Strip Cast AA3004 Aluminium Alloy

AA3004 aluminium alloy is most widely used in the beverage industry due to its excellent deep drawing properties and corrosion resistance. During deep drawing of the AA3004 sheets, the ‘earing phenomenon’ has to be minimized for economic advantage. In AA3004 and modified AA3004 alloys (like AA3104), this can be achieved by tailoring the crystallographic texture of the fully recrystallized sheet. Conventionally, AA3004 sheets are produced through direct chill (DC) casting route. In the present study, a twin roll cast AA3004 sheet is used for further processing (cold rolling and annealing). The texture comprised mainly of Cu ({112} 〈111〉), Brass ({110} 〈112〉) and S ({123} 〈634〉) orientations in the as-cast as well as cold rolled condition (Cu, Brass and S components being stronger in the cold rolled condition as compared to as-cast material). After complete recrystallization of 90 % cold rolled sheet, cube texture are deviated from ideal cube ({100} 〈001〉) (5°–10°) along with formation of Goss ({110} 〈001〉) and P{011} 〈122〉 components. This was in contrast to the DC casting route, where strong cube recrystallization texture is obtained.

Effect of rolling methods on microstructure, recrystallization texture and magnetic properties in a Fe–2.5%Si–0.52%Al non-oriented electrical steel

The effect of rolling methods on microstructure, recrystallization texture and magnetic properties in a Fe–2.5%Si–0.52%Al non-oriented electrical steel prepared with initial columnar grains is investigated. The results show that warm rolling promotes η-fiber nucleation and leads to strong η-fiber recrystallization texture at moderate strain, and the promotion effect is not limited in initial {110} <uvw> grains. At higher rolling strain, the intensity of η-fiber texture decreases. Warm rolling also promotes deformation bands with high-angle boundary, and the occurrence of deformation bands is explained with the change of active slip system. The highest B50 value and iron loss lower than 3W/kg are obtained in 0.5mm warm rolled sample, corresponding to moderate rolling strain, and λ-fiber texture lowers magnetic anisotropy.

Deformation textures of aluminum in a multilayered Ti/Al/Nb composite severely deformed by accumulative roll bonding

The accumulative roll bonding process was carried out to produce multilayered Ti/Al/Nb composites up to four cycles. Scanning electron microscopy, transmission electron microscopy electron backscattered diffraction and nanoindentation were employed to investigate the microstructural and texture evolution. A homogenous distribution of Ti/Nb necking layers in Al matrix was achieved after four ARB cycles. Grain refinement was observed to increase with increasing number of ARB cycles. The fraction of high-angle grain boundaries as also increased. Strong recrystallization texture appeared for high number of ARB cycles due to the adiabatic heat that occurs during ARB processing. The shear band at the Ti/Al interface reduced the intensity of the cold rolling fiber textures of Al. There was no evidence of shear component from the orientation distribution function results.

Novel Ti-base superelastic alloys with large recovery strain and excellent biocompatibility

In this study, a new Ti–Zr–Nb–Sn alloy system was developed as Ni-free biomedical superelastic alloys with a large recovery strain and excellent biocompatibility. Ti–18Zr–(9–16)Nb–(0–4)Sn alloys were prepared by an Ar arc melting method and the effect of composition on the crystal structure and superelastic properties was investigated. A large superelastic recovery strain of 6.0% was observed in Ti–18Zr–12.5Nb–2Sn, Ti–18Zr–11Nb–3Sn, and Ti–18Zr–9.5Nb–4Sn alloys subjected to cold-rolling and solution treatment. XRD results showed that the large recovery strain of Sn-added alloys is due to a combination effect of a large transformation strain and a strong recrystallization texture. The Ti–18Zr–11Nb–3Sn alloy exhibited excellent cyclic stability with an extremely narrow stress hysteresis about 20MPa. Cytocompatibility was also examined using three types of cell lines, murine fibroblast L929, human osteosarcoma SaOS-2, and human umbilical vein endothelial cell HUVEC and the results showed that the Ti–18Zr–11Nb–3Sn alloy exhibited larger cell covering ratios when compared with those of the Ti–50.5Ni alloy for all kinds of cells.

Transmission Kikuchi Diffraction study of texture and orientation development in nanostructured hard turning layers

A texture and orientation study was performed on the hard turning layers by utilizing newly developed Transmission Kikuchi Diffraction technique complemented by glancing angle X-ray diffraction and high resolution transmission electron microscopy (HRTEM). Results indicate that the hard turning process transforms the typical martensite lath/plate structure into equiaxed grains with low angle (<10°) boundaries. At lower cutting speeds, the texture was shear dominated while at high cutting speeds, the thermal transformation produced strong recrystallization texture. The results demonstrate that by simply manipulating the process conditions, hard turning could be utilized to tailor the surface nanostructures for enhanced service life.

The origin of annealing texture in a cold-rolled Incoloy 800H/HT after different strain paths

In this paper, we examine the nucleation and growth behavior of a highly deformed Incoloy 800H/HT. We also investigate the effect of rolling path (i.e. unidirectional and cross rolling) on the recrystallization mechanism and subsequent annealing texture of Incoloy 800H/HT. We used micro- and macro-texture measurements to investigate the evolution of texture components in various nucleation and growth stages. We studied the recrystallization kinetics by means of isothermal transformation plots based on recrystallized and softened fractions drawn from orientation imaging microscopy and microhardness measurements. Results show that the recrystallization kinetic after cross rolling (CR) is slower than after the uni-directional rolling (UDR) deformation. Due to different nucleation and growth mechanisms, these samples showed different recrystallization textures. CR samples exhibited a strong brass recrystallization texture while UDR samples showed a combination of Goss, copper and recrystallized brass ( 326 ) 〈 83 5 ¯ 〉 components.