Accumulative roll-bonding: first experience with a twin-roll cast AA8006 alloy
Introduction
The accumulative roll-bonding (ARB) is a relatively new method of severe plastic deformation proposed by Saito et al. [1]. The basic goal of ARB is to impose an extremely high plastic strain on the material, which results in structural refinement and strength increase without changing specimen dimensions. As can be seen from Fig. 1, the ARB process consists in repeating of cutting, stacking, and rolling of sheets.
It is known that ARB processing leads to the formation of a lamellar structure at high strains [2], and that the conversion of low-angle to high-angle boundaries dominates over grain refinement [3]. The ARB was successfully performed on commercial purity aluminum, some aluminum alloys and interstitial free (IF) steel [1], [2], [3]. Twin-roll cast (TRC) alloys, having a fine grain structure, have not yet been used for ARB.
The paper reports first experience with the application of ARB procedure in the preparation of ultra-fine grained (UFG) materials from a TRC Al–Fe–Mn–Si alloy (AA8006). The development of UFG microstructure during ARB processing was observed using scanning electron microscopy (electron backscatter diffraction—EBSD) and transmission electron microscopy (TEM). The strength of ARB sheets was evaluated by microhardness measurements.
Section snippets
Experimental details
The experimental material, a twin-roll cast strip of AA8006 alloy, was supplied by AL INVEST Břidličná, a.s., Czech Republic. Its chemical composition is in Table 1. In order to obtain an O-temper material, the strip was annealed for 0.5 h at 400 °C. Two pieces of the strip with dimensions of mm were stacked to form a 5 mm thick specimen. Before stacking, the surfaces of the strips were degreased (in tetrachlorethylene) and wire-brushed (stainless steel brush with wire of 0.3 mm in
EBSD
Fig. 2, Fig. 3 show EBSD orientation maps recorded on the longitudinal cross-sections of the sheets. In the initial material, a relatively large area of μm was scanned with a coarse step of 3 μm. Equiaxed grains with mean size of 16 μm were observed (Fig. 2). In order to detect the grain refinement resulting from ARB processing, a much finer step (0.2 μm) was used for the analysis of the processed samples.
In consequence, much smaller areas ( μm) were scanned to achieve a reasonable
Summary
First experience with ARB processing of TRC AA8006 alloy was acquired. After initial failures to achieve good sheet bonding, five cycles of ARB at 200 °C were successfully performed. The hardness of the alloy considerably increased after the first two cycles, but during subsequent ARB processing it rose only slightly. EBSD analysis showed important grain refinement even after two cycles of ARB. TEM observations confirmed that low-angle subgrain boundaries converted of to high-angle grain
Acknowledgements
This research was supported by the Grant Agency of the Czech Republic (project No. 106/03/0790), and in part by the EUREKA program (Project EU 2530 CONTCASTCALTRANS). The experimental material was kindly supplied by AL INVEST Břidličná, Czech Republic. Professor Claude Prioul, École Centrale Paris, kindly enabled the use of the EBSD facilities.
References (6)
- et al.
Acta Mater.
(1999) - et al.
Mater. Sci. Eng.
(2003) - et al.
Mater. Sci. Eng. A
(2001)
Cited by (32)
Effect of isothermal multidirectional compression on microstructure and mechanical properties of Al–Zn–Mg–Cu–Zr alloy with minor Sc addition
2024, Materials Chemistry and PhysicsEffect introduced high density of precipitates on the microstructural evolutions during multi-direction forging of Al–Zn–Mg–Cu alloy
2020, Materials Science and Engineering: ACitation Excerpt :The most commonly accepted mechanism for SPD grain refinement is based on the dislocation cell structure, which are formed at early stages of deformation and gradually transformed to the final fine grain structure. Equal channel angular (ECAP) [4–9], accumulative roll bonding (ARB) [10–15] and multi-directional forging (MDF) [16–22], are the most highly developed SPD processing technologies. Other processing technologies were also employed to refining grains, such as dual-straining by constrained groove pressing [23] and constrained groove pressing [24,25].
Evolution of microstructure and mechanical properties in 2014 and 6063 similar and dissimilar aluminium alloy laminates produced by accumulative roll bonding
2019, Journal of Alloys and CompoundsCitation Excerpt :ARB is one of the few SPD techniques that can be used to produce sheets of laminated monomaterials (further referred to as similar laminates) and laminated composites (further referred to as dissimilar laminates). Since its development [3], ARB was used to process a variety of metal sheets [4–6]. In order to optimize the material properties further, ARB lately is widely used to produce dissimilar laminates [7].
Effect of temperature and strain rate on the grain structure during the multi-directional forging of the Al[sbnd]Zn[sbnd]Mg[sbnd]Cu alloy
2019, Materials Science and Engineering: APrecipitation behavior of bulk nanocrystalline GW103K alloy induced by surface mechanical attrition treatment
2017, Journal of Alloys and CompoundsCitation Excerpt :Thus, there forms depth-dependent microstructure in the material after SMAT. The nanocrystalline grains achieved by SMAT involve numerous dislocation and sub grain boundaries on the surface, which are far higher than that obtained by Severe Plastic Deformation (SPD) method [16], including equal channel angular pressing (ECAP) [17], high-pressure torsion (HPT) [18], accumulative roll bonding (ARB) [19]. As compared with SPD ways, SMAT was proved to be an effective way to induce sufficient dislocation without strong texture in magnesium alloy.
Mechanical properties of an AM20 magnesium alloy processed by accumulative roll-bonding
2015, Materials Characterization