Cross-rolled Samples Research Articles

Effects of strain path on the microstructure, tensile properties, and formability of Al/Mg roll-bonded sheets

In this research, the experimental investigation of the change of the strain path on the microstructure, mechanical properties and the forming limit diagram of Al/Mg two-layer sheet made by roll bonding method has been performed. This research tries to make a two-layer Al/Mg sheet with a reduction ratio of 55% by using four single-pass and two-pass (the first pass with a reduction ratio of 40% and the second pass by changing the strain path in the form of direct rolling, reverse rolling and cross rolling) methods. The results show that the microstructure in cross rolling is more uniform than in other cases. No delamination is observed in fabricating the bilayer sheets with two passes. The best mechanical properties in terms of ultimate tensile strength and elongation are related to cross-rolled samples. Also, the cross rolling process causes a significant reduction in normal anisotropy. The comparison of formability for different conditions indicates the improvement of the forming limit diagram in cross rolling so that the amount of FLD0 for cross-rolled samples has increased by 15.6%, 13.8%, and 5.7%, respectively, compared to single-pass, two-pass direct rolling, and two-pass reverse rolling samples.

Microstructure, corrosion rate, and mechanical properties of unidirectionally and cross-rolled Mg-0.375Ga and Mg-0.750Ga alloys.

The effect of unidirectional and cross rolling on the corrosion rate, texture, tensile properties and hemolysis of the Mg-0.375Ga and Mg-0.750Ga alloys was evaluated. Pure Mg and as-cast alloys were processed by unidirectional and cross rolling at 400°C to obtain a total thickness reduction of 50%. The corrosion rate was measured by the weight loss method in simulated body fluid. Determination of the hemolysis percentage was carried out by direct contact of specimens with diluted blood. After hot rolling, the mechanical properties of the alloys were improved. The cross-rolled Mg-0.750Ga alloy showed the highest grain refinement (55 μm) and the highest ultimate tensile strength (240 MPa), however, lower elongation (13.9%) than the rolled Mg-0.375Ga alloy. While unidirectional rolling creates a strong basal texture, cross rolling weakens considerably this texture. The Ga addition weakens the basal texture. Corrosion rate of the Mg-Ga alloys was significantly reduced (<1 mm/yr) after heat treatment and hot rolling due the homogenization of the microstructure and the presence of gallium as alloying element. The cross-rolled samples showed higher corrosion than the heat-treated and unidirectionally rolled samples. After rolling, alloys showed hemolysis percentages between 7.1 and 9.3%, values lower than those presented by pure magnesium (>22.7%) and as-cast alloys (>24.2%); however, the alloys are still hemolytic (>5%).

CrCuFeMnNi high-entropy alloys for semisolid processing: The effect of copper on phase formation, melting behavior, and semisolid microstructure

High-entropy alloys containing Cu can lead to the formation of phases with lower melting temperatures and large solidification intervals, making them potential candidates for semisolid processing. Accordingly, in this study we aimed to investigate the influence of Cu content on the phase formation, melting behavior, and semisolid microstructure of CrCuFeMnNi alloys. Ingots with varying CrCu x FeMnNi compositions (x = 0, 0.5, 1, 1.5, 2, and 2.5) were arc-melted, cross-rolled, heated to reach the semisolid state, and water-quenched. Microstructural characterization involved scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The CrCuFeMnNi alloys were composed of one BCC phase, rich in Cr, and two FCC phases, one rich in Cu (FCC1) and the other with a more balanced composition (FCC2). The melting of the CrCuFeMnNi alloys was characterized by three thermal events, which corresponded to the melting of each phase. The solidification interval increased with the Cu content, and it was found that the studied alloys could be processed in the semisolid state at temperatures below 1100 °C. Therefore, the cross-rolled samples were isothermally heat-treated at 1080 °C for 300 s, resulting in globular microstructures. The chemical composition of the phases was modified after semisolid treatment as compared to the as-cast condition. The fraction of the BCC phase in the quenched microstructures did not change with the alloy composition; in contrast, the fraction of FCC1 increased, whereas that of FCC2 decreased with increasing Cu content. • The CrCuFeMnNi alloys were formed by three phases: one BCC and two FCC. • The CrCuFeMnNi alloys exhibited the same melting behavior. • The globularization process was efficient for all compositions. • The BCC fraction was the same regardless the alloy composition. • The FCC1 fraction increased and the FCC2 fraction decreased with Cu content.

Micro-mechanism of evolution of microstructure and texture in Ni-Fe alloys

A comprehensive investigation was carried out to explore the micro-mechanisms associated with the evolution of deformation microstructure and texture in Ni-Fe alloys during rolling. X-ray diffraction, electron back-scatter diffraction (EBSD) and Mössbauer spectroscopy as well as simulation methods involving crystal plasticity and molecular dynamics simulations were used to explore the mechanism of evolution. Pure Ni, Ni20wt.%Fe and Ni40wt.%Fe were rolled to true strain 3.0, following two different strain paths. Unidirectionally rolled Ni20wt.%Fe and Ni40wt.%Fe alloys show copper type texture, similar to that of pure Ni. By contrast, the cross rolled samples show the development of α-fibre along with A {110}<111> and cube {100}<001> orientations. Both Ni20Fe and Ni40Fe exhibit extensive shear banding in UDR as well as CR conditions, unlike pure Ni, which has been attributed to the appearance of two short-range ordered phases, Ni3Fe and NiFe. In case of UDR, the nature of shear banding is different in Ni20Fe and Ni40Fe alloys, while after CR both the alloys show similar microstructures displaying higher fraction of shear banding compared to UDR. Simulation results have indicated that larger number of slip systems are activated in case of CR compared to the UDR samples that leads to the formation of a weaker texture in the former. Some strain free grains have been observed near the shear banded regions, indicating that an extended recovery mechanism could be operative in Ni20Fe and Ni40Fe. This phenomenon was more pronounced when the fraction of shear bands was more.

Earing Prediction of Unidirectionally and Cross-rolled, Annealed AW-5056 Al Sheets from {h00} Pole Figures

Abstract Earing of deep drawn cups is an effective measure of plastic anisotropy. It is the result of crystallographic anisotropy, i.e. texture. There are several methods to predict earing, but all of these methods are rather complex. Furthermore, above a certain sheet thickness, deep drawing cannot be performed, and prediction methods fail since they are usually valid within a certain sheet thickness range. A new, simple method has been proposed to predict earing. Besides simplicity, another major benefit of the method is that it can be applied to a wide range of sheet thicknesses. The method has been previously applied for unidirectionally rolled and recrystallized and cross-rolled Al sheets. In the present manuscript, the proposed method is applied on the AW-5056 type, unidirectionally and cross-rolled, then annealed Al sheets having very weak (close to random) structure. It is shown that for such samples, the method predicts negligible earing. It is also revealed that for the 5056 type Al alloy, the differences in texture and earing between unidirectionally and cross-rolled samples become so small after annealing, that the benefit of cross rolling is negligible.

The dependence of the strain path on the microstructure, texture and mechanical properties of cryogenic rolled Al-Cu alloy

An investigation was conducted on Al-4%Cu alloy sheets to study the role of deformation path on the strength properties, evolution of microstructure and crystallographic texture during cryogenic rolling. Samples were rolled to two distinct thickness strains (50% and 75%) by unidirectional and cross rolling (bidirectional) routes. The strength and hardness properties were found to be more efficient in the cross rolled samples at 50% reduction than their counterparts rolled unidirectionally. Dynamic recovery was observed at higher rolling reductions on cross rolling. Microscopic features observed by EBSD revealed the occurrence of significant grain refinement on the samples rolled with a change of strain path. Also, the alteration of the rolling route resulted in distinct deformation textures and microstructures. TEM studies pointed out the scattered diffusion of the disintegrated dislocation cores and the redistribution of the second phase particles on higher rolling reductions with the change of strain path. Furthermore, the texture results showed a threefold increase on the Goss/Brass ratio which indicated the good fracture toughness behaviour of the cross rolled samples at lower reductions.

Significant influence of rolling modes on martensitic transformation, microstructural evolution and texture development in a 304 stainless steel

A 304 stainless steel was deformed by two different rolling modes (unidirectional cold rolling and cross rolling) at room temperature. The effects of rolling modes on martensitic transformation, microstructural evolution, and texture development were investigated. The results showed that martensitic transformation was enhanced significantly by cross rolling. The underlying reason was the increase in the amounts of nucleation sites for α′-martensite, i.e., intersections of shear bands. The transformation of austenite to martensite was found to be followed the sequence of γ → ε → α′ regardless of rolling modes. Rolling modes had great influences on deformation textures in both the remaining austenite and α′-martensite. For unidirectional cold-rolled samples, the main texture components of deformed austenite were Brass ({110}〈112〉) and S ({123}〈634〉) texture, while the α′-martensite phase exhibited {112}〈110〉, {223}〈121〉, and {554}〈225〉 orientations. However, ζ-fiber (〈110〉//ND) component, which was characterized by oscillation between Brass and G/B ({110}〈111〉) texture, was formed in remaining austenite during cross rolling, accompanied by a weakening of S component. Meanwhile, the α′-martensite phase in cross-rolled samples exhibited η-fiber (〈001〉//ND), and the dominant texture components were Rotated Cube ({001}〈110〉) and {001}〈160〉. The stability of the orientations during cross rolling can be responsible for texture development in both austenite and α′-martensite.

Effect of strain path during cold rolling on the microstructure, texture, and mechanical properties of AA2024 aluminum alloy

In this study, the effect of strain path during asymmetric cold rolling process on the microstructure, texture, and mechanical properties of AA2024 aluminum alloy was investigated. Optical microscopy (OM), scanning electron microscopy (SEM), and x-ray diffraction (XRD) were employed to characterize the microstructures and textures. The results showed that the average grain size of cold-rolled samples decreased compared to the as-received AA2024 alloy due to the occurrence of dynamic recrystallization (DRX). The number of DRX grains in the cross-rolled sample was larger than the unidirectional and reverse rolled samples owing to the higher stored strain energy and recrystallization rate of the cross-rolled AA2024. By performing the asymmetric cold rolling in all strain paths, the hardness increased due to increasing the stored strain energy and decreasing the grain size. The hardness and tensile strength of unidirectional and cross-rolled samples was equal. The presence of stronger hard orientations such as [111]∣∣RD in the unidirectional rolled sample compensated its higher grain size and lower stored energy. The overall intensity of components especially hard orientations of cross-rolled sample was much lower than other samples. On the other hand, some new and soft orientations, i.e. [313]∣∣ND and [323]∣∣TD, developed during cross rolling. These resulted in the production of an isotropic AA2024 sheet via asymmetric cross rolling. The fracture mode of deformed samples was a combination of ductile and brittle ruptures owing to increasing the stored strain energy and decreasing the ductility caused by asymmetric cold rolling. However, the contribution of ductile fracture in the cross-rolled sample was higher than the unidirectional and reverse rolled samples.

Anisotropic tensile and ratcheting behavior of commercially pure titanium processed via cross rolling and annealing

Microstructures, crystallographic textures, and mechanical properties for two different orientations along the rolling direction (RD) and transverse direction (TD) have been investigated in grade 2 commercially pure titanium sheet processed via cross rolling and annealing. The stress-strain curve has been simulated based on Viscoplastic self consistent (VPSC) model and relative slip/twin activity has been calculated for tensile and ratcheting deformation. The predicted slip/twin activity has been complemented with electron backscatter diffraction (EBSD) based deformation microstructure so as to shed light on the underlying micro-mechanism of anisotropic deformation behavior of cross rolled and annealed commercially pure titanium. The as received (AR) sheet exhibits equiaxed alpha grains with typical TD-split basal texture. After cross rolling, cross rolled (CR) sheet developed distinctly different RD-split texture. Both AR and CR sheet exhibit lower yield strength, higher elongation and higher ratcheting life for RD compared to TD orientation. However, the anisotropy in tensile properties have been found to be lower in CR sample, whereas the anisotropy in ratcheting properties have been found to be higher in CR sample compared to AR sample. VPSC simulation of tensile stress-strain response in the plastic regime reveals prism slip system {101¯0}<112¯0>, which acts as the primary mode of deformation in titanium gets suppressed with increase in strain, while basal and pyramidal slip activity rises in RD orientation and the situation is exactly reverse in case of TD orientation of cross rolled samples. In addition, electron backscatter diffraction based characterization of deformation microstructure reveals suppression of twinning activity too in CR samples. The manifestation of basal slip activity under controlled cyclic stress applied during ratcheting has been attributed for the augmentation of higher anisotropy in ratcheting response in CR samples.

Effect of cross-rolling on microstructure and texture evolution and tensile behavior of aluminium-copper-lithium (AA2195) alloy

The evolution of microstructure and crystallographic texture during thermo-mechanical processing and their effect on tensile behavior of Al-Cu-Li (AA2195) alloy were investigated in the present work. The initial hot rolled sheets were cold rolled by unidirectional rolling and cross-rolling. These sheets were annealed and imparted T6 (solution treatment + water quenching + aging) temper. Uni-directionally rolled samples exhibited typical copper texture which subsequently transformed to cube component after thermal treatment whereas, the cross-rolled sample exhibited brass texture which subsequently weakened upon thermal treatment. The difference in the precipitation characteristics resulted in transition from anisotropic to isotropic strength in cross rolled samples in heat treated condition. The strength anisotropy has been explained based on the average precipitation strengthening factor and accommodation tensor.

Asymmetric cross rolling (ACR): A novel technique for enhancement of Goss/Brass texture ratio in Al-Cu-Mg alloy

The present work focused on the effect of asymmetric cross rolling (ACR) process as a novel technique on microstructure and texture evolution of Al-Cu-Mg alloys. The microstructural observation and bulk texture from RD–TD plane of the initial and deformed samples were characterized by optical microscopy (OM) and X-ray diffraction (XRD). It was found that the deformed Al-Cu-Mg alloy consisted of strong Goss, Rotated Goss, Goss-Brass, and α-fiber textures. Usually, straight rolling leads to a significant strengthening of the Brass component with increasing strain in the Al-Cu-Mg alloy, but for asymmetrically cross rolled samples, the Goss orientation was stable after 40% deformation. Results showed that the ACR process was effective to intensify (up to 1.51 after 30% thickness reduction) the low Goss/Brass texture ratio often existing in the rolled Al-Cu-Mg alloy. During 30% ACR, the dynamic recrystallization (DRX) occurred, which led to increasing the intensity of Goss and Cube components and the fraction of extra high angle grain boundaries (EHAGBs).

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.

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 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.

Effect of Cross-Rolling on Microstructure, Texture and Magnetic Properties of Non-Oriented Electrical Steels

Hot rolled non-oriented electrical steel samples were subjected to cold cross-rolling of 80 % reduction in thickness. The cross-rolled samples were then annealed at 650, 750 and 850 oC for 1 hr, 2 hrs and 4 hrs respectively. The role of cross-rolling on microstructure, texture and magnetic properties of the samples after annealing has been investigated. Two different samples were used for the present investigation - one had higher Al content (sample S1) while the other had higher C, Si, Mn, P and S content (sample S2). It was observed that the sample S1 had higher grain size compared to sample S2 after annealing. The cross-rolling was observed to be controlled the texture developments in the samples and it was found that the texture factor was identical in all directions of the sample. The core losses in the samples were found to be decreased with increasing grain size of the samples.

Effect of crystallographic texture on precipitation induced anisotropy in an aluminium magnesium silicon alloy

Abstract The effect of crystallographic texture on precipitation induced anisotropy in yield strength of an aluminium magnesium silicon alloy was investigated. Solutionized samples were subjected to unidirectional and multi-step cross rolling to yield distinct crystallographic textures in the Al–Mg–Si alloy. The rolled sheets were then subjected to annealing followed by second solutionizing treatment to provide sheets with similar grain size and dislocation content but distinct texture. Ageing experiments were carried out on these sheets at 443 K for different time intervals. It was observed that the evolution of anisotropy in yield strength of the age hardened alloy depends on texture. The difference in age hardening response brought about by varying initial texture controls the evolution of anisotropy in mechanical properties of the alloy. This was manifested in terms of transition from anisotropic to isotropic mechanical properties in the unidirectionally rolled samples after peak ageing. On the contrary, a transition from isotropic to anisotropic yield behaviour was observed for multi-step cross rolled samples. This is attributed to enhanced precipitation hardening in crystallographically softer orientations compared to crystallographically harder orientations.

Effect of deformation route and intermediate annealing on magnetic anisotropy and magnetic properties of a 1 wt% Si non-oriented electrical steel

In the present work the influence of intermediate annealing and the strain path during a two-stage cold rolling on the microstructure and texture of a 1wt% Si non-oriented electrical steel was investigated. Different processing conditions were tasted to develop favorable texture and better understand the relation between texture and important magnetic properties. The texture parameter (TP) was defined as “theta fiber/gamma fiber” ratio. The results showed that the samples with the highest TP have the lowest magnetic anisotropy. Also average magnetocrystalline energy was calculated and it was demonstrated that the lowest energy can be correlated with the highest “theta fiber/gamma fiber” ratio. Regardless of the condition of intermediate annealing process, the uni-directional rolling produced very similar texture parameter (~2). However, the cross rolled samples have very different texture parameters upon intermediate annealing. The cross rolled samples after intermediate annealing at 650°C have the highest texture parameter (~3). The proposed thermo-mechanical processing allow diminishing gamma fiber which is deleterious for magnetic properties of non-oriented electrical steels.

Influence of cross-rolling on the micro-texture and biodegradation of pure iron as biodegradable material for medical implants

Iron-based biodegradable metals have been shown to present high potential in cardiac, vascular, orthopaedic and dental in adults, as well as paediatric, applications. These require suitable mechanical properties, adequate biocompatibility while guaranteeing a low toxicity of degradation products. For example, in cardiac applications, stents need to be made by homogeneous and isotropic materials in order to prevent sudden failures which would impair the deployment site. Besides, the presence of precipitates and pores, chemical inhomogeneity or other anisotropic microstructural defects may trigger stress concentration phenomena responsible for the early collapse of the device. Metal manufacturing processes play a fundamental role towards the final microstructure and mechanical properties of the materials. The present work assesses the effect of mode of rolling on the micro-texture evolution, mechanical properties and biodegradation behaviour of polycrystalline pure iron. Results indicated that cross-rolled samples recrystallized with lower rates than the straight-rolled ones due to a reduction in dislocation density content and an increase in intensity of {100} crystallographic plane which stores less energy of deformation responsible for primary recrystallization. The degradation resulted to be more uniform for cross-rolled samples, while the corrosion rates of cross-rolled and straight-rolled samples did not show relevant differences in simulated body solution. Finally, this work shows that an adequate compromise between biodegradation rate, strength and ductility could be achieved by modulating the deformation mode during cold rolling.

The effect of thermo-mechanical processing on grain boundary character distribution in Incoloy 800H/HT

In this study, we applied a thermo-mechanical process to alter the grain boundary characteristic distribution (GBCD) with a view to the feasibility of grain boundary engineering in Incoloy 800H/HT. In order to optimize the GBCD through increasing the low Σ coincidence-site lattice (CSL) boundaries, we applied various thickness reductions with two different rolling modes followed by annealing. We used Electron Backscattered Diffraction (EBSD) to analyze the GBCD and CSL boundaries. We found that the coincidence-site lattice boundaries, particularly Σ3 and its variants, increased with the pre-deformation level in cross-rolled (CR) samples. In contrast, the fraction of these CSL boundaries had an optimum in 50% reduction for unidirectionally rolled (UDR) samples. In fact, different Σ3n interactions led to different GBCD in UDR and CR processed samples. Low to medium deformation with UDR and medium to high deformation with CR on the Incoloy 800H/HT samples showed potential for grain boundary engineering.

Effect of thermo-mechanical processing on texture evolution in austenitic stainless steel 316L

In this study we implemented two rolling modes to investigate the strain path effect on deformation and annealing textures of austenitic stainless steel 316L. We applied unidirectional rolling and cross-rolling to achieve up to a 90% reduction in thickness. Results show that for deformed austenite, Brass, Goss and γ-fibre were the main texture components in the unidirectional rolled sample, while Brass was the dominant texture in the cross-rolled sample. In addition, rotated Copper and rotated Cube were the main textures of martensite after 90% reduction for unidirectional rolled and cross-rolled samples, respectively. Results also show that recrystallization texture has a direct correlation to that of deformed austenite since transformed martensite reversion was athermal. After recrystallization, Brass and a combination of Brass and Goss were the dominant textures for cross-rolled and unidirectional rolled samples, respectively.