Cold-rolled Aluminium Research Articles

Characterization of rough self-affine surfaces by electromagnetic wave scattering

We study the scattering of electromagnetic waves from metallic self-affine surfaces, and review earlier approximative results for the angular distribution of the scattered light (the mean differential reflection coefficient). Furthermore, experimental scattering data for industrial cold-rolled aluminium surfaces that show self-affine scaling invariance are presented. Comparison between these experimental data and approximative analytic and rigorous numerical simulation results shows very good agreement over the dominating angular interval where most of the scattered power is distributed. The excellent quality of this agreement suggests that light scattering can be used as a cheap, robust and versatile (inverse scattering) tool for characterizing self-affine metallic surfaces, i.e. used to estimate roughness exponents as well as topothesies and the related slope parameters.

Influence of Local Lattice Orientation on Grain Subdivision in 40% Cold-Rolled Aluminium

Influence of Local Lattice Orientation on Grain Subdivision in 40% Cold-Rolled Aluminium

Development of plastic strain heterogeneities on cold-rolled aluminium alloys during in situ shear tests inside an SEM

Shear tests inside an SEM were performed to study plastic localisation phenomena on cold rolled aluminium alloys 1200, 3004 and 5182. Strain distribution was obtained by image analysis of micro-grids deposited on the sample surface prior to the tests. Macroscopic shear bands initiate from the samples ends and close to the grips after the load maximum. Their spreading through the whole sample occurs by nucleation and propagation of microscopic shear bands, and depends on the alloy and on the direction of shear. The link between the different scales are discussed, from the dislocation microstructures to the macroscopic scale. The global boundary conditions govern the distribution of spatial heterogeneities, but the local hardening behaviour controls the localisation sharpness.

Quantitative analysis of grain subdivision in cold rolled aluminium

A procedure is proposed for a statistical characterisation of deformed microstructures from the data collected using Orientation Imaging Microscopy (OIM). This procedure has been applied for a characterisation of 352 grains in commercial purity aluminium cold-rolled to a reduction of 40%. The results demonstrate the different behaviour of grains with different orientations: (i) grains having orientations near the {001}<100> and {025}<100> components develop orientation gradients over distances of 10–20 μm; (ii) grains with orientations close to the {205}<502> component form fragments with relatively large misorientations, and (iii) grains within the β-fibre form fragments with relatively small misorientations. The experimental results are compared to previous observations by transmission electron microscopy (TEM) and good agreement is found. Finally, possible applications of the present observations for advanced texture modelling are discussed.

Measurement of average texture of cold-rolled aluminium sheet by electron back-scattering diffraction: a comparison with neutron diffraction

Measurements of the average texture on sheet of commercial pure aluminium have been performed using neutron diffraction and electron back-scattering diffraction (EBSD). Orientation distribution function maps have been calculated and compared. The results show a good correspondence provided that the data from the EBSD measurements are corrected according to a texture index versus inverted number of measurement procedure. Most errors are probably related to differences in investigated volume and calculation technique and to the fact that the microstructure was difficult for EBSD measurements.

Comparison of fracture in sheets of low pressure gas (LPG) steel and aluminium alloys

Fracture behaviour under different stress states of four heats of hot rolled low pressure gas (LPG) grade steel and three 1 mm thick cold rolled aluminium alloys (Al–Cu–Mg, Al–Mg and Al–Mn) is compared. Dimple fracture was present in all four materials but the dimples were larger and of more uniform size in LPG steel compared with those present in the Al-alloys. Depending on the relative strength of pearlite and pearlite–matrix interface, failure in LPG steel was either transgranular or ductile intergranular. In the Al-alloys, particle–matrix decohesion was always responsible for dimple formation and transgranular fracture. In the Al–Cu–Mg and Al–Mg alloys a bimodal dimple size distribution, traceable to precipitates of two different sizes, was present but in the Al–Mn alloy the dimple size was larger and of nearly the same size. The results are explained in terms of composition, microstructure and mechanical properties of the alloys.

Structural evolution and phase formation in cold-rolled aluminum–nickel multilayers

Multilayer samples of nickel and aluminum with the compositions of Al–20 at% Ni and Al–25 at% Ni were prepared by the repeated folding and cold rolling (F&R) of elemental foils. Characterization by X-ray diffraction, scanning electron microscopy and transmission electron microscopy/selected-area electron diffraction reveals that the rolling procedure results in a decrease in thickness of the elemental layers to below 0.1 μm and a reduction in grain size to below 50 nm, but does not induce formation of an intermediate phase. Differential scanning calorimetry (DSC) measurements on samples subjected to different numbers of F&R cycles show double exotherms related to an initial nucleation and lateral growth and a subsequent thickening of reactively formed Al 3Ni. The DSC data agree qualitatively with predictions of an existing kinetic model for multilayer reactions, but a decisively improved quantitative fit is obtained when a distribution of layer spacings is considered, rather than a well-defined modulation wavelength. The modified kinetic model can be inverted to yield information on the evolution of the distribution of layer sizes during deformation from DSC data.

Light scattering from cold rolled aluminum surfaces

We present experimental light scattering measurements from aluminum surfaces obtained by cold rolling. We show that our results are consistent with a scale invariant description of the roughness of these surfaces. The roughness parameters that we obtain from the light scattering experiment are consistent with those obtained from atomic force microscopy measurements.

A new model for recrystallization of heavily cold-rolled aluminum using orientation-dependent stored energy

A model for recrystallization of heavily cold-rolled aluminum is proposed. This model has been tested employing a three-dimensional modified Monte-Carlo procedure, which incorporates a full description of microstructure and texture. The necessary input parameters such as orientation-dependent stored deformation energy have been obtained using X-ray diffraction. In order to overcome the complexity of the deformed microstructure, the orientation and location of the nuclei are selected by a set of proposed conditions based on texture and scatter in the measured orientation-dependent stored energies in the cold-rolled and stress-relieved states. The rate of reduction of stored energy plays a major role in deciding the rate of nucleation of new grains with different orientations. The unique misorientation distribution that cube grains have in the cold-rolled matrix is responsible for the enhanced growth rate of the nucleated cube grains. The simulated results are compared with the experimental data. Agreement of these results suggests that in the development of the cube texture both oriented nucleation and oriented growth play an important role.

Analysis of surface roughness of cold-rolled aluminium foil

This paper describes a detailed analysis of the surface finish of aluminium foil which has been cold-rolled under industrial conditions in the mixed lubrication regime. The foil was rolled with freshly ground rolls at a constant speed for the first pass and at a wide range of speeds for the second pass. Samples were collected after the second pass. For comparison, samples were also collected after rolling with worn rolls. Surface replicas of the rolls were taken with surface replicating tape. The surface roughness of the strip samples and roll surface replicas was measured with a three-dimensional non-contact interferometric profilometer. The spectrum of the surface roughness was analysed by the fast Fourier transform method to identify the way in which different wavelengths of roughness behave. Theory suggests that longer wavelengths of roughness should be crushed more easily. This was confirmed by results. A new image analysis technique has been developed to identify and quantify the area of the micro-pits. To differentiate between these pits and grind marks transferred from the rolls, the height information was first filtered in the rolling direction using a digital filter. The low-frequency component of the surface roughness, which represents the contribution from the roll marks, was subtracted off to leave the pits. Results showed a significant decrease in pit area during the pass schedule, while there was a significant increase in pit area with increasing rolling speed during a single pass.

Finite element analysis of damage evolution and the prediction of the limiting draw ratio in textured aluminum sheets

Void nucleation and growth models have been incorporated into an elasto-plastic finite element code together with an anisotropic fourth-order strain rate potential so that damage evolution during the deep drawing of textured aluminum sheets can be analyzed. The fourth-order strain rate potential is based on the Taylor model of crystal plasticity and therefore takes the presence of texture into account. The damage evolution is modeled in terms of void nucleation and growth during deformation. Strain-induced and stress-controlled nucleation models were employed in conjunction with the Cocks and Ashby growth model to calculate the increase in void volume fraction. The influence of plastic anisotropy on damage is discussed together with the roles of void nucleation and growth on damage evolution for cold rolled and cold rolled annealed aluminum sheets. It is shown that the growth of voids as opposed to their nucleation plays a very important role in damage formation during the development of localized necks. More attention should therefore be paid to void nucleation and growth in the analysis of localized necking and fracture during sheet metal forming.

Through-thickness texture gradients in cold-rolled aluminum

The through-thickness texture variations in ∼40 pct cold-rolled polycrystalline aluminum were studied using X-ray diffraction and the electron backscattering pattern (EBSP) technique. The influence of the roll-gap geometry and of sequences of small and intermediate draughts on the development of deformation textures in multipass rolling was considered. It was found that similar textures were formed near the surface and in the central layers of all specimens, while, in the intermediate layers of different plates, different textures were observed. Small draughts gave rise to the shear texture in the intermediate layers, while no pronounced shear texture was revealed anywhere through the thickness of plates rolled with intermediate draughts. It was found that small-draught rolling only has a pronounced effect on the texture if it accounts for a significant strain in the rolling schedule. It was found, furthermore, that nonuniformity of the initial recrystallization texture may be retained in the texture after ∼40 pct rolling.

Correction for Liu and Hansen, Macroscopic and microscopic subdivision of a cold-rolled aluminium single crystal of cubic orientation

You have accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Liu Q. and Hansen N. 1999Correction for Liu and Hansen, Macroscopic and microscopic subdivision of a cold-rolled aluminium single crystal of cubic orientationProc. R. Soc. Lond. A.4554384http://doi.org/10.1098/rspa.1998.1001SectionYou have accessCorrection for Liu and Hansen, Macroscopic and microscopic subdivision of a cold-rolled aluminium single crystal of cubic orientation Q. Liu Q. Liu Google Scholar Find this author on PubMed Search for more papers by this author and N. Hansen N. Hansen Google Scholar Find this author on PubMed Search for more papers by this author Q. Liu Q. Liu Google Scholar Find this author on PubMed Search for more papers by this author and N. Hansen N. Hansen Google Scholar Find this author on PubMed Search for more papers by this author Published:08 December 1999https://doi.org/10.1098/rspa.1998.1001This article corrects the followingResearch ArticleMacroscopic and microscopic subdivison of a cold–rolled aluminium single crystal of cubic orientationhttps://doi.org/10.1098/rspa.1998.0271 Qing Liu and Niels Hansen volume 454issue 1978journalTitle Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences08 October 1998AbstractCorrection for ‘Macroscopic and microscopic subdivision of a cold-rolled aluminium single crystal of cubic orientation’ by Q. Liu and N. Hansen (Proc. R. Soc. Lond. A 454, 2555–2591. (doi: 10.1098/rspa.1998.0271)).Figure 10 on p. 2570 was printed with data missing. The figure is reproduced in full below. Previous ArticleNext Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsCited by Milner J, Bunget C, Abu-Farha F, Kurfess T and Hammond V (2013) Modeling tensile strength of materials processed by accumulative roll bonding, Journal of Manufacturing Processes, 10.1016/j.jmapro.2013.02.001, 15:2, (219-226), Online publication date: 1-Apr-2013. Related articlesMacroscopic and microscopic subdivison of a cold–rolled aluminium single crystal of cubic orientation08 October 1998Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences This Issue08 December 1999Volume 455Issue 1992 Article InformationDOI:https://doi.org/10.1098/rspa.1998.1001Published by:Royal SocietyPrint ISSN:1364-5021Online ISSN:1471-2946History: Published online08/12/1999Published in print08/12/1999 License: Citations and impact PDF Download

Modeling composition/processing/property relationships in a cold-rolled aluminum alloy

Two semi-empirical models have been developed that allow the yield strength and tensile strength of 3105 aluminum alloy sheet, cold rolled to various H1x tempers, to be predicted with reasonable accuracy directly from the ingot composition. Expansion of these models also enables the calculation of the percent cold reductions required to produce tensile properties specified for these tempers also from the ingot composition.

Scaling of Misorientation Angle Distributions

The measurement of misorientation angle distributions following different amounts of deformation in cold-rolled aluminum and nickel and compressed stainless steel is reported. The scaling of the dislocation cell boundary misorientation angle distributions is studied. Surprisingly, the distributions for the small to large strain regimes for aluminum, 304L stainless steel, nickel, and copper (taken from the literature) appear to be identical. Hence the distributions may be ``universal.'' These results have significant implications for the development of dislocation based deformation models.

FEM simulation of the forming of textured aluminum sheets

A texture-based fourth order strain-rate potential was used directly in an elastoplastic finite element code (ABAQUS) to model sheet metal forming. The method is based on the Taylor model of crystal plasticity and therefore takes the presence of texture into consideration. The deep drawing of cold-rolled and annealed aluminum sheet was simulated using this code in conjunction with a specially developed UMAT subroutine. The full geometry of deep drawing, including the disposition of the tools and the effect of friction, was taken into account in the simulations and both shell and brick elements were employed. The influences of element type, as well as of friction and blank holder force, are discussed. The thickness variations induced by deep drawing are also described. Reasonable agreement was obtained between the predicted and measured earing profiles for an annealed aluminum sheet. The steps to be followed to bring about further improvements in the accuracy of the simulations are also discussed.

Macroscopic and microscopic subdivison of a cold–rolled aluminium single crystal of cubic orientation

An aluminium single crystal of cube orientation has been rolled to 15, 30 and 50% reductions under controlled homogeneous rolling conditions. The deformation structure of the rolled specimens was investigated by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) over several scales of magnification. The local crystallographic orientations have been measured by an automatic electron back scattering patterns (EBSP) technique and a semiautomatic TEM method. Orientation image maps based on the local orientation data have been used to reveal the evolution of the deformation structure during rolling. It is observed that by an opposite rotation around transverse direction (TD) the crystal was subdivided into four macroscopic bands, termed matrix bands in the present paper, which are parallel to the rolling plane. Between the four bands there are three transition bands in which the orientation changes continuously from that of a matrix band to that of the adjoining one. A model based on the idea of location–dependent shear strain caused by geometric and friction effects together with a plasticity analysis has been used to explain the macroscopic subdivision of the crystal. In addition to the macroscopic subdivision, a microscopic subdivision by the formation of cell–blocks within the matrix bands and a cell structure within transition bands has also been observed. A difference related to shear amplitude difference between the active slip systems changing continuously across the crystal has been observed. Both the macroscopic orientation of the dislocation boundaries and the misorientation angles and axes across dislocation boundaries are analysed and it is found that Frank9s formula is a useful tool in analysing the dislocation boundaries formed during deformation.

Mechanisms of surface deformation during cold rolling of aluminium

The main surface features found during cold rolling of initially twin-rolled cast aluminium are grooves, gorges, shingles, cross hatches and rolling ridges. Grooves–shingles are formed at the exit side of the neutral plane during casting and these are deformed into gorges in the first pass and the shingle is smeared over the cavity. A large number of shingles are formed in the second pass from steps in the surface resulting in interfaces within the surface region. Due to the following extension of the sheet and the shift in rolling direction these interfaces will be extended and new interfaces formed by additional smearing out of steps, resulting in a laminated structure in the surface. Cross hatches are formed in these laminated areas. Later passes cause the cross hatches to grow and new ones to be formed. © 1998 Chapman & Hall

The effective threshold of fatigue crack propagation in aluminium alloys I. The influence of yield stress and chemical composition

Abstract The thresholds of effective stress intensity range ΔK eff th of a recrystallized and cold-rolled aluminium (pure), and aluminium alloys 6061, 7020 and 7075 were studied. A special technique to determine ΔK eff th very accurately was applied. The measured ΔK eff th value was about 0.85 MPa m1/2 in all alloys. The significant difference in the yield stress (it varies between 30 and 630 MPa) and the chemical composition does not influence ΔK eff th.

The effective threshold of fatigue crack propagation in aluminium alloys. I. The influence of yield stress and chemical composition

Abstract The thresholds of effective stress intensity range ΔK eff th of a recrystallized and cold-rolled aluminium (pure), and aluminium alloys 6061, 7020 and 7075 were studied. A special technique to determine ΔK eff th very accurately was applied. The measured ΔK eff th value was about 0.85 MPa m1/2 in all alloys. The significant difference in the yield stress (it varies between 30 and 630 MPa) and the chemical composition does not influence ΔK eff th.