Multi-step Cross Rolling Research Articles

Mechanical properties of cross rolled CoCrFeMnNi high entropy alloy

In recent years, there has been a significant interest in high-entropy alloys (HEAs) due to their unique compositions, microstructures, and the ability to customize their properties. This study investigated the microstructure and deformation behaviour of the CoCrFeMnNi HEA under homogenised and rolled conditions. Two rolling methods were employed, namely two-step cross-rolling (TSCR) and multi-step cross-rolling (MSCR). Texture analysis revealed the development of Brass (Bs) {1 10} < 112 > and Goss (G) {011} < 100 > texture components in the samples, with an equivalent strain of 1.609. Notably, the MSCR technique involved rotating the samples at a 45° angle around the normal direction (ND) during alternate passes, which was a novel approach in this study. TSCR samples exhibited the formation of dense lamellar bands, while MSCR samples displayed dense dislocations forming a cell block-type structure. Vickers hardness testing revealed differing hardness outcomes as a result of varying deformation levels in samples. Specifically, the TSCR sample with 80% deformation exhibited the highest hardness, while the 50% deformed MSCR sample displayed a comparatively lower hardness. In the context of room-temperature tensile tests, the 80% deformed TSCR sample showed higher ultimate tensile strength but lower ductility. In contrast, the 80% deformed MSCR sample exhibited a slightly lower ultimate tensile strength but higher percentage elongation compared to the TSCR sample. These findings suggest that multi-step cross-rolling can effectively enhance the strength and ductility of HEAs, providing valuable insights for optimizing their mechanical properties. The microstructural and mechanical characterization presented in this study contributes to understanding deformation mechanisms and property optimization strategies in HEAs, thereby supporting their potential applications across various industries.

Correlation of microstructure, texture and intermetallic particles during multi-step cross-rolling and annealing in a strip-cast AA8011 alloy

In multi-step cross rolling (MSCR), twin roll cast (TRC)/strip-cast AA8011 aluminum sheet was cold-rolled up to 72 % thickness reduction by rotating +/- 90º with respect to normal direction (ND) after each rolling pass. The intermetallics particle size after MSCR got reduced to ∼ 0.5–3 µm compared to unidirectional cold rolling (UCR) ∼ 1.5 – 4.5 µm (Kumar et al. 2018) after the same thickness reduction of 72 %. Subsequently, it was annealed at 375 ºC for varying times (1–240 min). Both investigations (UCR/MSCR) showed no removal of centerline segregation (CLS) of Al-Fe-Si intermetallics. After 72 % cold rolling (UCR/MSCR), deformation texture (i.e., Brass (Bs) {110} < 112 > , copper (Cu) {112} < 111 > , Goss {110} < 011 > and S {123} < 634 > ) strengthened at the expense of Cube {100} < 001 > . However, cube improves during annealing at 375 ºC after MSCR than UCR. Moreover, it was observed that particle-stimulated nucleation (PSN) (intermetallics particle size ≥ 2 µm) played an important role in promoting random texture. For instance, the % volume fraction of Brass, Copper, Goss, S, Cube were 6.1 %, 5.3 %, 3.7 %, 9.0 %, 4.8 % (Kumar et al. 2018) and 6.5 %, 3.6 %, 1.9 %, 7.7 %, 5.3 % for UCR and MSCR, respectively. Hence, MSCR effectively reduces intermetallic particles size, decreases the overall anisotropy and improves the recrystallization texture (especially Cube component of texture) of TRC AA8011 aluminum alloy.

Extensive Plastic Deformation to Improve the Mechanical Properties and Electrical Conductivity of Copper through Multistep Cross Rolling

Extensive Plastic Deformation to Improve the Mechanical Properties and Electrical Conductivity of Copper through Multistep Cross Rolling

The effect of severe cryogenic plastic deformation and change in strain path on nanostructured copper through multistep cross rolling

The trade-off between strength, ductility, and electrical conductivity of pure copper restricts its application in recent technologies and hence modification of microstructure through plastic deformation at cryogenic temperature was used to address this contradiction. In this research article, commercially available pure copper was subjected to cryogenic severe plastic deformation to obtain ultra-fine grains (UFG) through a multistep cross rolling process. The change in strain path and deformation at cryogenic temperature has a strong impact on the mechanical properties and microstructure of the rolled copper plates since rolling at cryogenic temperature suppresses the dynamic recovery and enables grain refinement. Mechanical properties such as yield strength (Ys), ultimate tensile strength (UTS), and microhardness increased by 158%, 80%, and 57% respectively. A very good optimum combination of electrical conductivity of 86% IACS and formability of 10.49 I.E. was obtained. A weak brass (Bs) oriented texture was observed due to continuous change of strain path.

Correlation of strain path and crystallographic texture with electrochemical behavior of Ti-15V-3Cr-3Sn-3Al alloy

Effect of strain path and crystallographic texture on electrochemical properties of cold-rolled Ti-15V-3Cr-3Sn-3Al (all elements in weight%, designated as Ti-15333) alloy has been studied in the present investigation. The as-received specimens with and without solution annealing (SA) were subjected to different strain paths to reduction ratio (RR) of 40% and 80%. The microstructure showed the presence of shear bands (SBs) in all the deformed specimens and its fraction increased with increase in the RR. With the increase in deformation, α- and γ- fibers were observed in all the specimens. Electrochemical potentio-dynamic tests followed by open circuit voltage were used to investigate the passivity and pitting corrosion in 3.5% NaCl solution for both the undeformed (as-received, SA) and deformed Ti-15333 alloy specimens. A complementary assessment was employed to analyze the influence of work-hardening on passivity and pitting corrosion behaviors of Ti-15333 alloy systematically, combined with additional investigation of electrochemical impedance spectroscopy (EIS). High corrosion resistance was observed for the SA specimen than non-SA (as-received) specimen. Increase in the RR from 40% to 80% increased the corrosion rate for all the strain paths, except multi-step cross-rolled (MSCR). Corrosion resistance of the 80% deformed specimens were dependent on both the evolved microstructure (SBs, grain fragmentation) as well as crystallographic texture. Multi-step cross rolling resulted in the formation of a strong Rotated Cube ({100}<110>) texture, which was expected to be the reason for its enhanced corrosion resistance.

Effect of modes of rolling on evolution of texture in pure copper and some copper base alloys

Abstract The present study was aimed at examining the effect of modes of rolling and subsequent annealing on yield locus anisotropy and its dependence on microstructure and texture. The materials, pure Cu, Cu(Cr) alloy and Cu(P) alloy, have been subjected to equal amount of cold rolling reductions by unidirectional, two-step cross rolling and multistep cross rolling and consequent changes in yield loci has been examined. The yield loci have been determined by the Knoop hardness method. The results show that the alloys exhibit marked anisotropy after direct as well as cross rolling. Annealing of the rolled materials brings down the extent of anisotropy.

Multistep Cross Rolling of UNS S32101 Steel: Microstructure, Texture, and Magnetic Properties

In the present study, effect of multistep cross rolling (MSCR) on microstructure, texture, and magnetic properties has been investigated for UNS S32101 steel. UNS S32101 steel consisting of almost equal proportion of ferrite and austenite was 80% cold cross rolled in multiple steps. The microstructures were characterized using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD), while crystallographic texture was determined by x-ray diffraction (XRD). Microstructure showed decrease in band thickness and spacing for both austenite and ferrite with increased cold-rolling reduction. Lenticular bulges were the main feature of microstructure after 80% cold rolling, indicating the presence of strain-induced martensite (SIM). Hysteresis loops were also measured in order to characterize other parameters associated with deformation and SIM. The magnetic anisotropy decreased, while coercivity (Hc), area under the B-H loop and magnetic losses increased with an increase in cold-rolling reduction. Hc was found to be directly proportional to the amount of reduction during cold rolling and inversely proportional to equivalent circle grain size. As-received sample showed strong cube ({100} ) with strong Brass ({110} ) in austenite and strong α (rolling direction, RD// ) and γ (normal direction, ND// ) fibers in ferrite. For 80% rolling, strong Brass and Goss ({110} ) were developed in austenite, while strong rotated cube ({100) ) and γ-fiber were obtained in ferrite.

Texture development during multi-step cross rolling of a β titanium alloy: Experiments and simulations

In the present work, microstructure and texture evolution during multi-step cross rolling of a β-Ti alloy was investigated. The as-received samples were cross rolled in a laboratory rolling mill to 20%, 40%, 60% and 80% thickness reduction. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe the changes in microstructure, while the changes in bulk texture were evaluated using X-ray diffraction. The as-received sample consisted of equiaxed as well as elongated grains. Equivalent circle average grain size (AGS) and the average band thickness (ABT) along normal direction (ND) for as-received β-Ti sample was 50 ± 3 μm and 27 ± 1.8 μm respectively. The AGS and ABT decreased with increase in cold rolling reduction (for 80% cold rolled sample ABT was 7.5 ± 2.3 μm). Another important feature was the presence of strain localizations in the cold rolled samples, the frequency of which increased with increase in strain. The as-received sample showed the presence of α (rolling direction RD//<110>) and γ (ND//<111>) fibers. At highest strain (80% cold rolling), rotated cube ({100}<110>) component was found to be significantly stronger than the γ-fiber texture. Visco-Plastic Self Consistent (VPSC) model was used for the simulation of texture during cold cross rolling. Qualitatively, full constraint VPSC model was found to match reasonably well with the experimental data. α-Fiber, γ-fiber and rotated cube were over estimated in the VPSC texture predictions.

Evolution of Deformation Texture in Low Modulus β Ti-34Nb-2Ta-(0, 3)Zr-0.5O Alloys

Ti-Nb-based low modulus metastable β-titanium alloys are popular choice for orthopedic implant materials. The performance of these materials could be affected by variation in crystallographic texture developed during processing. In the present study, texture evolution during unidirectional rolling and multi-step cross-rolling of the alloys Ti-34Nb-2Ta-3Zr-0.5O (TNTZO) and Ti-34Nb-2Ta-0.5O (TNTO) (in wt pct) has been studied. In both the alloys, the rolling texture is characterized by the absence of RD∥〈110〉 fiber, and cross-rolling leads to a stronger texture than unidirectional rolling. However, the prominent texture components in the cross-rolled condition are different for the two alloys. The TNTZO alloy shows the formation of a strong γ-fiber (ND∥〈111〉) along with {001}〈110〉 components while in TNTO, the texture is dominated by strong {001}〈110〉 component. These experimental results have been analyzed by simulations using viscoplastic self-consistent model and further validated by microstructural analysis using electron back scattered diffraction (EBSD). The deformation texture evolution has been attributed to a predominantly $$ \left\{ {11\overline{2} } \right\}\left\langle {111} \right\rangle $$ slip. The simulated texture of Ti-34Nb-2Ta-0.5O alloy shows a minor deviation from the experimental texture, which can be related to the reduced stability of this alloy due to the absence of Zr.

Incremental Forming of the Al-Li Alloy AA2195: Role of Texture and Microstructure

This study deals with the evolution of crystallographic texture during secondary processing of aluminium-lithium alloy AA2195 sheets and its effect on the single-point incremental forming (SPIF) process. Significantly different textures were generated in AA2195 alloy sheets by the unidirectional rolling (UDR) and multi-step cross-rolling (MSCR) processes followed by subsequent annealing. The differently textured sheets were then subjected to the SPIF process. For UDR processed sheets, the texture was the strong copper type (Cu-type), whereas in MSCR processed sheets, the texture comprised weak fibres. The UDR samples with strong texture experienced cracking during incremental forming, whereas the MSCR samples could be formed without any cracks. Detailed analyses of the microstructure and texture were performed at various locations on the incrementally formed part to understand the deformation micromechanism at specific locations on the formed component.

Microstructure and texture development in Ti-15V-3Cr-3Sn-3Al alloy – Possible role of strain path

In the present investigation, evolution of microstructure and texture was studied for a β titanium alloy during cold rolling (unidirectional rolling (UDR) and cross rolling (multi-step cross rolling (MSCR) and two step cross rolling). For both UDR and MSCR of initially hot rolled alloy consisting of elongated and equiaxed grain structure, the occurrence of shear bands inside the grains was the main feature of the microstructure. The density of these shear bands was dependent on the cold rolling reduction and strain path and was found to be orientation dependent. Shear bands preferentially occurred in γ-fiber (normal direction (ND)//〈111〉) oriented grains. The regions with shear bands had higher hardness than the regions without shear bands, and {111}〈112〉 component of the γ-fiber was found to be more susceptible to formation of shear bands. The orientation dependence of these shear bands was analyzed within the framework of Dillamore's plastic instability criterion. During UDR, strong α and γ-fibers were observed after highest strain (ε = 1.6), while strong rotated cube ({100}〈110〉) texture developed after MSCR at highest strain (ε = 1.6). The volume fraction of both α and γ fibers gradually increased with the increase in cold rolling reduction during UDR. For MSCR, the rotated cube component gradually increased with increase in cold rolling reduction. In solution annealed β-Ti alloy with equiaxed grain structure, α and γ fibers were formed after highest strain (ε = 1.6) during UDR. However, due to large grain size, both α and γ fibers were discontinuous. The texture development was found to be more strongly dependent on the strain path than the initial microstructure during cold rolling.

A fractal approach to predict the oxidation and corrosion behavior of a grain boundary engineered low SFE high entropy alloy

The current study presents a method to predict the oxidation and corrosion properties in a grain boundary engineered low stacking fault energy (SFE) FCC high entropy alloy (HEA) Ni14Cr21.5Co21.5Fe21.5Mn21.5 through fractal analysis. Two thermo-mechanical processing (TMP) routes namely, unidirectional rolling (UDR) and multistep cross rolling (MSCR) with intermediate annealing, were employed to enhance the percentage of coincident site lattice (CSL) boundaries and break the random boundary network (RBN) in the alloy. Electron backscattered diffraction (EBSD) was utilized to analyze the microstructure and local texture of the samples before and after subjecting the samples to TMP. Fractal analysis (box-method) was carried out to analyze and quantify the RBN in the processed samples. Potentiodynamic polarization experiments were carried out to study the corrosion resistance as a function of CSL boundaries in the processed samples. Thermogravimetric analysis (TGA) was carried out to study the oxidation behavior in the samples. Elemental segregation in the oxide layer was also analyzed using Energy dispersive spectroscopy (EDS) line scan analysis. In the final part of the study, empirical relationships were established between fractal number, oxide layer thickness, and corrosion rate respectively. It was observed that Fractal numbers could be used as a powerful and reliable tool to predict some of the grain boundary character dependent properties like corrosion and oxidation in the alloy system under study.

Deciphering the Possible Role of Strain Path on the Evolution of Microstructure, Texture, and Magnetic Properties in a Fe-Cr-Ni Alloy

In the present work, the influence of strain path on the evolution of microstructure, crystallographic texture, and magnetic properties of a two-phase Fe-Cr-Ni alloy was investigated. The Fe-Cr-Ni alloy had nearly equal proportion of austenite and ferrite and was cold rolled up to a true strain of 1.6 (thickness reduction) using two different strain paths—unidirectional rolling and multi-step cross rolling. The microstructures were characterized by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD), while crystallographic textures were determined using X-ray diffraction. For magnetic characterization, B-H loops and M-H curves were measured and magnetic force microscopy was performed. After unidirectional rolling, ferrite showed the presence of strong α-fiber (rolling direction, RD//〈110〉) and austenite showed strong brass type texture (consisting of Brass (Bs) ({110}〈112〉), Goss ({110}〈001〉), and S ({123}〈634〉)). After multi-step cross rolling, strong rotated cube ({100}〈110〉) was developed in ferrite, while austenite showed ND (normal direction) rotated brass (~ 10 deg) texture. The strain-induced martensite (SIM) was found to be higher in unidirectionally rolled samples than multi-step cross-rolled samples. The coherently diffracting domain size, micro-strain, coercivity, and core loss also showed a strong correlation with strain and strain path. More strain was partitioned into austenite than ferrite during deformation (unidirectional as well as cross rolling). Further, the strain partitioning (in both austenite and ferrite) was found to be higher in unidirectionally rolled samples.

Effect of strain path change on the texture evolution after cold rolling and recrystallization of Nickel-40 wt. %Cobalt alloy

Effect of change in strain path during rolling and its role in the development of crystallographic texture after deformation and then after recrystallization has been studied for Ni-40wt%Co which is a medium stacking fault energy (SFE) material. Results indicate that textures developed after unidirectional rolling and multi-step cross-rolling are quite different which also leads to different texture evolution after recrystallization. Microstructure of both UDR and cross rolled sample shows band type of feature within the grain having lesser band density for cross rolled samples. After recrystallization unidirectionally rolled sample shows bimodal whereas cross rolled sample shows equiaxed grain size distribution. But all the samples show large fraction of annealing twins. It has been shown that in all cases formation of annealing twins have large influence on the texture transition after recrystallization.

Effect of Strain Path on Texture Evolution in Cold Rolled Pure Titanium

The cold rolling texture evolution as a function of strain path in pure titanium with initial typical recrystallized texture has been studied using viscoplastic self-consistent simulations. Three different strain paths, namely unidirectional rolling, two-step cross rolling and multi-step cross rolling have been employed to investigate the effect of strain path change on the evolution of deformation texture. The simulation results indicate that the activation of predominant prismatic slip in unidirectional rolling sample results in the formation of commonly cold rolling fiber texture RD//&lt;10-10&gt; in pure titanium, whereas the increased activity of basal slip over that of prismatic slip is responsible for the strong ND//&lt;hkil&gt; fiber texture in the two cross rolled samples.

Effects of Mode of Deformation and Extent of Reduction on Evolution of {111}-Fiber During Cold Rolling of Ni-16Cr Alloy

The high ratio of relative resolved shear stress on a twin to planar slip system results in microstructural latent hardening (some kind of overshooting) by the twin system on the primary slip planes, which leads to development of the {111}-fiber in Ni-16Cr alloy. The development of {111}-fiber starts as early as around 16 pct cold reduction in Ni-16Cr alloy and persists with maximum average intensity ranging from 35 to 40 pct additional deformation, i.e., around 50 pct cold reduction in unidirectional (U) and two-step cross (T)-rolling modes. In between 50 and 68 pct reductions in U and T modes, the fiber becomes unstable and starts disappearing. However, in multistep cross (M) rolling, the {111}-fiber formation starts late, i.e., at around 50 pct reduction, and maintains its stability up to additional deformation ranging from 35 to 40 pct, i.e., around 90 pct cold reduction. Thus, the life of {111}-fiber remains stable only within the range from 35 to 40 pct intermediate deformation during cold rolling of Ni-16Cr alloy irrespective of modes of rolling. However, the start and end of fiber stabilities depend on the modes of deformation by rolling. The maximum average intensity of {111}-fiber that can be attained in Ni-16Cr alloy is around 3.6× random in any of the deformation modes.

Effect of strain path on the evolution of microstructure, texture and tensile properties of WE43 alloy

Hot rolling of extruded and solutionized WE43 alloy was carried out at 400°C through different strain paths such as unidirectional rolling (UDR) and multistep cross rolling (MSCR). The effect of strain path on the evolution of microstructure and texture was investigated. The grain size was ∼ 7µm and 18µm after hot rolling of UDR and MSCR samples, respectively. A strong basal texture was observed during rolling which is independent of the strain path of the samples and the recrystallization mechanism was identified to be continuous dynamic recovery and recrystallization type. Further, the texture of the deformed and recrystallized grains was observed to be same. Hence, the texture was simulated successfully using visco-plastic self-consistent (VPSC) simulation. The VPSC simulation of UDR sample showed the dominant activity of basal and prismatic slip system up to a true strain of ∼ 0.5 and after that pyramidal < c + a > activity dominants, whereas MSCR sample showed the combined activity of basal and pyramidal < c + a > up to a true strain of ∼ 0.5 and later on basal activity dominants on further deformation. The room temperature tensile testing showed that the yield strength of MSCR sample was greater than UDR sample except along RD of UDR sample and the tensile strength was more for MSCR compared to UDR sample which suggests that higher volume fraction of metastable precipitates in MSCR than UDR sample during high temperature rolling. The higher volume fraction of metastable precipitates was attributed to lower dislocation activity on prismatic planes of MSCR compared to UDR sample during hot rolling. The current VPSC simulation showed that the prismatic slip activity was four times higher in UDR than MSCR sample. A decrease in mean free path of dislocations by the presence of metastable precipitates led to higher tensile strength of MSCR compared to UDR sample. The mean free path of dislocations increased from RD to TD and hence, results in a decrease in tensile strength from RD to TD of both the samples.

Texture development during cross rolling of a dual-phase Fe–Cr–Ni alloy: experiments and simulations

Texture development during multi-step cross rolling of a dual-phase Fe–Cr–Ni alloy has been investigated. X-ray diffraction was used to investigate changes in crystallographic texture of both the constituent phases (austenite and ferrite) through changes in orientation distribution function. After deformation, rotated brass (rotated along φ1, i.e. the sample normal direction ND), along with a weak cube texture was observed in austenite, while a strong rotated cube texture was obtained in ferrite. Texture was also simulated for various strains using a co-deformation model by self-consistent visco-plastic (VPSC) formulation. Simulations showed strong rotated brass texture in austenite and a strongly rotated cube, α-fibre (sample rolling direction RD //<1 1 0>) and γ-fibre (ND //<1 1 1>) in ferrite after highest strain (εt = 1.6). VPSC models could not effectively capture the change in crystallographic texture during cross rolling. In ferrite, simulations showed an overestimation of γ-fibre component and an underestimation of rotated cube component. Simulated texture of austenite, on the other hand, showed an overestimation of rotated brass with an absence of cube component. The results are rationalised based on the possible role of shear banding and activation of non-octahedral slip system during cross rolling, both of which are not incorporated in conventional VPSC models.

Effect of rolling mode and annealing temperature on microstructure and texture of commercially pure-titanium

The evolution of microstructure and texture of commercially pure titanium (CP-Ti) developed by unidirectional rolling (UDR) and multi-step cross rolling (MSCR) followed by annealing treatment at different temperatures was investigated by X-ray bulk texture measurement and electron backscatter diffraction (EBSD) technique. Recrystallisation was complete at about 873K for both UDR and MSCR samples. In UDR mode, the TD-split type deformation texture remain unchanged whereas in MSCR mode, near basal deformation texture transformed to RD split type basal texture after annealing. This has been attributed to the non-oriented nucleation of recrystallised grains and growth of (0002)<112¯0> (major) texture component of the deformed sample by consuming (0002)<101¯0> (minor) texture component in UDR. Whereas in MSCR sample, oriented nucleation of (0002)<101¯0> and (0002)<112¯0> basal texture components occur which compete at the growth stage leading to weak recrystallisation texture compared to UDR. The distinct texture evolution with similar grain size after recrystallisation leads to similar hardness for UDR and MSCR samples.

Low temperature cross-rolling to modify grain boundary character distribution and its effect on sensitization of SS304

Sensitization of austenitic stainless steels is well-known in the temperature range of 400–800°C. This effect can be lowered by the introduction of low-Σ coincident site lattice (CSL) boundaries in the material. In present work, 304 stainless steel was thermo-mechanically processed to obtain microstructures containing varied fractions of low-Σ CSL boundaries. Processing consisted of multi-step cross rolling at −41°C followed by a short heat treatment at 1000°C. In order to understand the effect of grain boundary character distribution (GBCD) on sensitization behavior, firstly, heating condition corresponding to the maximum degree of sensitization (DOS) was found by comparing double loop electro-chemical potentiodynamic reactivation (DL-EPR) plots for all the samples, which were given sensitization heat treatment at 600°C for various time. Later, a relation between the GBCD and DOS was established by conducting DL-EPR test on all the processed samples. Low-temperature cross rolling was found to be effective in keeping the fraction of low angle grain boundaries (LAGBs) low and ensuring equi-axed grain structure. The sample, which was given low strain followed by short heat treatment, showed highest fraction of CSL boundaries among all other conditions. Grain size was found to decrease with increase in pre-strain. The results indicated that sensitization was inversely related to the fraction of CSL boundaries and grain size, while it was directly related to the fraction of random high angle grain boundaries (HAGBs). It was also found that sensitization was weakly related to the fraction of LAGBs indicating that these boundaries did not show “special” behavior, as they do in many other grain boundary related phenomenon.