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Study on the post-rolling direction of severely plastic deformed Aluminum-Manganese-Silicon alloy

Jandaghi M. R., Pouraliakbar H., Khalaj G., Khalaj M. J., Heidarzadeh A.

Archives of Civil and Mechanical Engineering

2016

Vol. 16, no. 4

876--887

Constrained groove pressing (CGP) as a severe plastic deformation (SPD) technique was applied on Al-Mn-Si sheets. In the following, direct- and cross-rolling were employed as supplementary processing in order to investigate the rolling-direction effect on CGPed sheets. The in-depth characterization of microstructural evolutions were employed using polarized light microscope and scanning electron microscope. Williamson–Hall analysis method was applied on X-ray diffraction (XRD) patterns of specimens. Analysis of XRD results revealed that post-rolling of CGPed sheets induced dynamic recrystallization (DRX) due to massive dislocations’ accumulation which follows by crystallite growth. The largest crystallite size which was 619 nm achieved after direct-rolling through the rolling strain of 1.27. Maximum acquired peak intensity ratio for rolled sheets was for (220) crystallographic plane similar to annealed one. Also, post-rolling had altered the distinguished plane from (111) for CGPed sheets into (220). Mechanical characteristics of specimens were examined using hardness and tension tests. Based on the obtained results, direct-rolling of CGPed samples was more susceptible for strength enhancement compared to cross-rolling. Optimum achieved values for yield and ultimate tensile strength were 155 and 197 MPa, respectively. Rolling in the both longitudinal and cross directions had almost similar effect on the final attained hardness.

Numerical Modelling of Constrained Groove Pressing with Deform 3D Software

Kesner D., Fišer P., Zrnik J., Cieslar M., Kešner D.

Computer Methods in Materials Science

2007

Vol. 7, No. 1

130-135

The Constrained Groove Pressing (CGP) is one of the many forming processes, which are used for preparation of ultrafine-grained structure in materials. With this technique, it is possible to manufacture bulk fine-grained products using a wide range of steels and alloys. The finite element method (FEM) modelling may be used for verification of design tool parameters, for optimization of the shape of the CGP-tools and for optimization of the forming process. It provides significant information on the effects of the tool geometry, material properties and friction upon the flow of material. In this study, numerical modelling has been used for investigation of forming with dies of different groove shapes, various sample thicknesses and two different specimen materials (steel and aluminum alloy). The distribution and amount of effective strain and the magnitudes and changes in forming forces were evaluated. The calculation has shown the differences between the alternative forming configurations in terms of the distribution and amount of effective strain. The computation results were used as a basis for design of optimum-shaped tools and verifying the technological process. This optimum alternative has been experimentally tested. The plates prior to CGP had a coarse-grained recrystallized structure with large scatter in grain size. Specimens were forged with up to four strokes, each stroke introducing the strain of about 0.7 in the deformed segments. The impact of the experimental forming upon microstructure development was investigated with light microscopy, scanning electron and transmission electron microscopy of thin foils. Mechanical properties of selected specimens from different regions of the plates were determined by tensile tests. The results show that the Constrained Groove Pressing with one completed pass resulted in formation of non-uniform finer microstructures with some new grains formed by intensive deformation and dynamic recrystallization process. The presence of low tensile and compressive strain in flat segments of specimens, resulted as well in grain refining process, as suggested by numerical simulation, has been confirmed by transmisson electron microscopy observation. However, higher number of passes is required to further homogenize and refine the microstructure.

Kucie w matrycy ze zbieżnymi rowkami (CGP) jest jednym z wielu procesów przeróbki plastycznej, który wykorzystywany i jest przede wszystkim do przygotowania drobnoziarnistej struktury materiałowej. Za pomocą tej technologii możliwe jest wytwarzanie wielu drobnoziarnistych materiałów o dużej objętości.Metoda elementów skończonych może być wykorzystana do weryfikacji parametrów projektu narzędzia w celu optymalizacji kształtu narzędzi CGP oraz parametrów procesu. Dzięki temu możliwe jest uzyskanie znaczących informacji na temat wpływu kształtu narzędzi, właściwości materiałowych oraz tarcia na płynięcie materiału podczas odkształcenia. Niniejszy artykuł przedstawia wykorzystanie modelowania numerycznego w celu analizy procesu przeróbki dla matryc o różnym kształcie wyżłobień, zróżnicowanej grubości próbki oraz dla dwóch różnych materiałów (stal oraz stop aluminium). Otrzymane rezultaty pokazują, iż w wyniku zastosowania 'metody CGP otrzymano niejednolitą strukturę drobnoziarnistą z zarodkującymi nowymi ziarnami, które powstały jako efekt silnego odkształcenia oraz procesu dynamicznej rekrystalizacji.