Papers by Author: Terence G. Langdon

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Authors: Marco J. Starink, Shun Cai Wang, Nong Gao, H. Singh Ubhi, Cheng Xu, Terence G. Langdon
Abstract: The texture and grain boundary evolution during equal channel angular pressing (ECAP) of a spray-cast Al-7034 (Al-Zn-Mg-Cu) alloy containing intermetallic particles with a range of sizes was studied through electron backscatter diffraction (EBSD). Up to 8 passes of ECAP using route Bc were employed. The initial ECAP pass leads to the development of low angle grain boundaries and subsequent passes lead to a relatively rapid increase in the fraction of high angle grain boundaries. Before ECAP, the material possessed a strong <111> and <100> fibre texture. On ECAP, the <111> fibre texture component is mostly retained but the <100> fibre develops to a Cube texture after the first ECAP pass. Goss textures form from about 4 passes of ECAP.
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Authors: Megumi Kawasaki, Cheng Xu, Terence G. Langdon
Abstract: A commercial aluminum 7034 alloy, produced by spray casting and having an initial grain size of ~2.1 μm, was subjected to equal-channel angular pressing (ECAP) through six passes at 473 K. In the as-pressed condition, the microstructure was reasonably homogeneous and the grain size was reduced to an ultrafine grain size of ~0.3 μm. This alloy contains MgZn2 and Al3Zr precipitates which restrict grain growth. In tensile testing at 673 K after processing by ECAP, an elongation of >1000% was achieved at a strain rate of 1.0 × 10-2 s-1 corresponding to high strain rate superplasticity. Quantitative cavity measurements were conducted on the specimens after tensile testing for both the as-received condition and after ECAP. These measurements reveal a significant number of small cavities in the samples and especially in the sample that exhibited a very high elongation. This paper describes the morphology of cavity development in the spray-cast aluminum alloy in both the as-received and as-pressed condition.
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Authors: Minoru Furukawa, Yukihide Fukuda, Keiichiro Oh-ishi, Z. Horita, Terence G. Langdon
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Authors: Minoru Furukawa, Yukihide Fukuda, Keiichiro Oh-ishi, Z. Horita, Terence G. Langdon
Abstract: This paper describes experiments in which high purity copper single crystals of two different orientations were processed for one pass by equal-channel angular pressing (ECAP) and the deformed structures were examined using optical microscopy (OM), orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The first single crystal (0° specimen) was oriented within the entrance channel of the die so that the {111} slip plane and the <110> slip direction were parallel to the theoretical shear plane and shear direction, respectively. The second crystal (20° specimen) was oriented with the {111} slip plane and the <110> slip direction rotated by 20° in a clockwise sense from the theoretical shear plane and shear direction, respectively. For the 0° specimen, after passing through the shear plane there were two crystallographic orientations representing the initial orientation and an orientation rotated by 60° in a counter-clockwise sense from the initial orientation. For the 20° specimen, there was an orientation rotated by 20° in a counter-clockwise sense from the initial orientation after passing through the shear plane.
113
Authors: Aicha Loucif, Thierry Baudin, François Brisset, Roberto B. Figueiredo, Rafik Chemam, Terence G. Langdon
Abstract: This investigation uses electron backscatter diffraction (EBSD) to study the development of microtexture with increasing deformation in an AlMgSi alloy having an initial grain size of about 150 µm subjected to high pressure torsion (HPT) up to a total of 5 turns. An homogeneous microstructure was achieved throughout the disc sample at high strains with the formation of ultra-fine grains. Observations based on orientation distribution function (ODF) calculation reveals the presence of the torsion texture components often reported in the literature for f.c.c. materials. In particular, the C {001}<110> component was found to be dominant. Furthermore, no significant change in the texture sharpness was observed by increasing the strain.
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Authors: Patrick B. Berbon, Minoru Furukawa, Z. Horita, Minoru Nemoto, Nikolai K. Tsenev, Ruslan Valiev, Terence G. Langdon
1013
Authors: Minoru Furukawa, Z. Horita, Terence G. Langdon
Abstract: This paper describes experiments in which high purity aluminum (Al) and copper (Cu) single crystals of different crystallographic orientations were processed for one pass by equal-channel angular pressing (ECAP). The deformed structures were examined using optical microscopy (OM), orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The results for Al single crystals are compared with those for Cu single crystals.
2853
Authors: Genki Sakai, Katsuaki Nakamura, Z. Horita, Terence G. Langdon
Abstract: High pressure torsion (HPT) is a well-known procedure to impart severe plastic deformation (SPD) into metallic materials. It was reported that HPT produces grain sizes finer than those using other SPD processes such as equal-channel angular pressing (ECAP). However, the application of HPT has been restricted to thin disk samples. In this study, an HPT process was developed for use with bulk samples. This process is designated as Bulk-HPT for comparison with conventional Disk-HPT. Cylindrical samples of an Al-3%Mg-0.2%Sc alloy having dimensions of 10 mm in diameter and 8.6 mm in height were prepared for Bulk-HPT. The samples were strained under a pressure of 1 GPa for 2 turns at room temperature. Microstructural observations revealed that the samples contained regions having a grain size of ~130 nm. Tensile testing showed a superplastic ductility ~480 % at 673 K with an initial strain rate of 3.3x10-2 s-1.
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