Cross-rolled Material Research Articles

Enhancing Mechanical Properties of Poly(p-phenylene sulfide) by Biaxial Deformation Using Cross-Rolling and Subsequent Annealing

The effect of thermal treatment on the mechanical performance of biaxially oriented poly(p-phenylene sulfide) by cold roll milling was studied. It was found that the ductility of the cross-rolled material could be further enhanced by annealing at temperatures above Tg and the yield strength could be enhanced by annealing at temperatures below Tg with a partial loss in ductility. Two-dimensional wide-angle X-ray diffraction patterns suggested a reduced crystallinity in the rolled material and showed that the crystal structure of the unrolled material could be partially recovered by annealing above Tg; however, scattering patterns adjacent to the crystalline reflections persisted with heat treatment. Modulated differential scanning calorimetry (MDSC) and broadband dielectric spectroscopy indicated that cross-rolling altered the kinetics of the cold-crystallization process. MDSC and dynamic mechanical analysis measured a reduction in Tg suggesting enhanced molecular mobility as an outcome of cross-rolling. After annealing at temperatures well beyond Tg, a large reduction in elongation to failure was observed, and the material could not cold draw. These results suggest that a two-stage process involving plastic deformation by roll milling followed by annealing treatment may be used to commercially produce high toughness and yield strength sheet products from commercially available resins.

Microstructure and texture development in CoCrNi medium entropy alloy processed by severe warm cross-rolling and annealing

The effect of cross-rolling on microstructure and texture evolution in equiatomic CoCrNi medium entropy alloy (MEA) was investigated in the present work. For this purpose, the MEA was warm-rolled to 90% reduction in thickness at 400 °C by unidirectional and different cross-rolling routes. The heavily deformed specimens were further annealed at temperatures varying from 700 °C to 1200 °C. The development of fine-scale microstructures and profuse shear band formation was confirmed in all the processed materials. Compared to unidirectional processed material, the different cross-rolled materials showed greater propensity for forming intersecting shear bands. Higher hardness in the different cross-rolled materials was consistent with finer microstructure and abundant shear bands. Unidirectional processed material showed weak brass ({110}<112>) component, whereas the different cross-rolled material showed rotated brass components. Upon annealing, the different cross-rolled materials showed smaller grain sizes than the unidirectional processed material due to more abundant potential nucleation sites. The recrystallization texture of the different processed materials showed retention of the deformation texture components. High fractions of random components indicated weak recrystallization texture, contributed by the absence of preferential nucleation and growth and profuse annealing twin formation.

Cross-rolling mediated microstructure and texture evolution in severely cold-rolled and annealed ultrafine pearlite

Effect of cross-rolling on the evolution of microstructure and texture in pearlite was investigated in the present work. For this purpose, near pearlitic steel was cold-rolled to 95% reduction by unidirectional cold-rolling (UCR) and different cross-rolling routes. The UCR processed material showed a predominantly lamellar structure, while the microstructure development in selected cross-rolled materials was featured by the presence of profuse shear bands and severely bent lamellae. While the UCR processed materials showed the presence of the typical RD (//〈110〉) and ND (//〈111〉) fibers, the texture formation in different cross-rolled materials was featured by the strong presence of a {001}〈110〉 component of the RD-fiber. The presence of the prominent {001}<110 > component could be explained by the stability of this component under cross-rolling. Recrystallization resulted in progressive spheroidization of the cementite. The pinning of the high angle boundaries by the cementite particles hindered the long-range migration of boundaries, thus inhibiting typical discontinuous recrystallization but favoring a recovery dominated softening process. The recrystallization textures in different cross-rolled materials were featured by the retention of deformation texture, namely the prominent {001}<110 > component of the RD-fiber, which amply corroborated a recovery dominated mechanism. Extended annealing resulted in the onset of abnormal grain growth in selected cross-rolled materials, which appeared to affect the microtexture, while the global texture remained mostly unaffected.

Effect of strain path on microstructure and texture formation in cold-rolled and annealed FCC equiatomic CoCrFeMnNi high entropy alloy

The effect of strain path on microstructure and texture formation in an equiatomic CoCrFeMnNi high entropy alloy was investigated. For this purpose, the alloy was cold-rolled to 90% reduction in thickness (total equivalent strain (εeq) ∼2.65) using unidirectional cold-rolling (UCR) and different cross-rolling routes. In the MSCCR route, the samples were rotated by 90° around the ND in between each pass. In the TSCCR(90°) and TSCCR(45°) routes, the samples were deformed by unidirectional rolling to half of the εeq (∼1.3) in the first step and the rest half of the strain (εeq ∼1.3) was imparted after rotation around the ND by 90° and 45°, respectively. The development of deformation microstructures in all the processing routes were characterized by fine lamellar type structure intercepted by inclined shear bands. The TSCCR(45°) processed material appeared to be most prone to shear band formation. The UCR processed material showed brass type texture, while the textures of different cross-rolled materials were featured by different rotated brass components. Upon annealing, the UCR processed material showed the lowest grain size while the highest grain size was observed in the TSCCR(45°) processed material. This indicated greater available nucleation sites in the UCR processed material as compared to the TSCCR(45°) processed material. The differences in annealed grain size was presumably higher due to substructure destabilization and misorientation build-up diminishing the number of potential nuclei in the TSCCR(45°) processed material. The annealing textures of the differently processed materials were featured by the presence of α-fiber (ND//<110>) and absence of preferential nucleation and growth.

Texture Evolution in Nanocrystalline Nickel: Critical Role of Strain Path

The effect of strain path change during rolling on the evolution of deformation texture has been studied for nanocrystalline (nc) nickel. An orthogonal change in strain path, as imparted by alternating rolling and transverse directions, leads to a texture with a strong Bs {110}〈112〉 component. The microstructural features, after large deformation, show distinct grain morphology for the cross-rolled material. Crystal plasticity simulations, based on viscoplastic self-consistent model, indicate that slip involving partial dislocation plays a vital role in accommodating plastic deformation during the initial stages of rolling. The brass-type texture evolved after cross rolling to large strains is attributed to change in strain path.

The effect of starting grain size on the evolution of microstructure and texture in nickel during processing by cross-rolling

Abstract Nickel sheets having starting grain sizes of 36 μm (fine grained starting material) and 800 μm (coarse grained starting material) were deformed by unidirectional and cross cold rolling routes up to 90% reduction in thickness. Unidirectional rolled sheets developed pure metal or copper type deformation texture irrespective of the starting grain size. However, significant differences could be observed in the texture of the two materials processed by cross-rolling. The most remarkable difference in the texture of the cross-rolled materials was much stronger Brass ({011} ) and rotated Brass ({011} 7 4 _ 4 > ) components in the fine grained starting material as compared to the coarse grained starting material. The observed differences in texture during processing by the cross-rolling route might be attributed to the different grain subdivision behavior in coarse grained starting material due to large starting grain size which correlated well with the very diffuse and fragmented microstructure developed in this material.

Enhancement of Grain Refinement and Formability of Cross-Roll-Rolled Ni-10Cr Alloy

This study evaluated the enhancement of microstructural and mechanical properties of a cross rolled Ni-10Cr alloy, comparing with conventionally rolled material. Cold rolling was carried out to 90% thickness reduction and the specimens were subsequently annealed at for 30 min to obtain a fully recrystallized microstructure. Cross roll rolling was carried out at a tilted roll mill condition of from the transverse direction in the RD-TD plane. In order to observe the deformed microstructures of the cold rolled materials, transmission electron microscopy was employed. For annealed materials after rolling, in order to investigate the grain boundary characteristic distributions, an electron back-scattering diffraction technique was applied. Application of cold rolling to the Ni-10Cr alloy contributed to notable grain refinement, and consequently the average grain size was refined from 135 in the initial material to 9.4 and 4.2 in conventionally rolled and cross rolled materials, respectively, thus showing more significantly refined grains in the cross rolled material. This refined grain size led to enhanced mechanical properties such as yield and tensile strengths, with slightly higher values in the cross rolled material. Furthermore, the //ND texture in the CRR material was better developed compared to that of the CR material, which contributed to enhanced mechanical properties and formability.

Origin of the {h 1 1 }&lt;1/h,1,2&gt; Fiber in Single Phase Ferrite Steels

In the present work, the oriented nucleation origin of the recrystallized {h11}&lt;1/h,1,2&gt; fibre is characterized. Aiming to investigate the substructural evolution of &lt;110&gt;//RD fibre grains and {001}&lt;110&gt; grains in particular, a detailed microstructure and texture analysis is performed by high resolution orientation scanning microscopy on a cross-rolled sample. The reason to work with cross-rolled material is the increased incidence of rotated cube orientations after cross rolling. The present data have revealed the presence in the deformed substructure of a crystallite volume that has rotated towards the {311}&lt;136&gt; component in the interior of &lt;110&gt;//RD fibre grains as a result of a grain fragmentation process. Preliminary simulations of the deformation texture suggested that the observed orientation fragmentation might be produced by strain localizations of a shear band nature.

Role of strain path change in texture development

This work describes the role of strain path change during cold rolling in texture development of pure Cu and Cu(P) alloys. The unidirectional- and two-step cross-rolled materials exhibit different textures. The detailed analysis of these results in terms of the adequate deformation mechanisms is also presented.