Microtexture Development of Niobium in a Multilayered Ti/Al/Nb Composite Produced by Accumulative Roll Bonding
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ODUCTION
THE accumulative roll bonding technique (ARB), which was first developed by Saito et al.,[1] is a severe plastic deformation process that has attracted the interest of both scientific and industrial communities. During the repeated folding and rolling process, large amounts of plastic strain were introduced into the same or different metallic materials without changing the initial dimension, while the structural refinement and mechanical property enhancement were achieved.[2,3] Due to its simplicity and low cost, ARB can be used as an appropriate technique to process multilayered composites.[4] The texture evolution is always very important for cold-rolled samples. However, the texture development in samples developed by the ARB process has not been studied extensively. It is known that during rolling, the metals deform in homogeneously through thickness due to the large amount of shear strain that is introduced into the surface and subsurface regions.[5] Furthermore, half of the surface region is folded to the center in the next ARB cycle and such a procedure is repeated as the cycles of ARB increase. The shear strain distribution through thickness becomes very complicated in ARB,[5] which introduces more complex features to the rolling
PENG QU, formerly Ph.D. Student with the Department of Metallurgical & Materials Engineering, The University of Alabama, 360 H.M. Comer Hall, Box 870202, Tuscaloosa, AL 35487-0202, is now Research Assistant with The University of Alabama at Birmingham, Birmingham, AL. LIMING ZHOU, Metallurgical Engineer, is with the Nidec Motor Corporation, St Louis, MO. HUI XU, Senior Engineer, is with the Kulicke & Soffa Industries Inc., Fort Washington, PA. VIOLA L. ACOFF, Head and Professor, is with the Department of Metallurgical & Materials Engineering, The University of Alabama. Contact e-mail: vacoff@eng.ua.edu Manuscript submitted February 21, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS A
texture compared to conventional roll bonding. Furthermore, the more complex texture change for dissimilar metal ARB process has been rarely researched. The ARB process followed by annealing was successfully used in our previous research for the fabrication of multilayered TiAl and TiAlNb elemental foils.[6,7] The ARB technique was proven to be beneficial for grain refinement, and the high strain introduced into the multilayered metals promoted the diffusion between dissimilar sheets. However, the texture evolution during the ARB process for Ti, Al, and Nb sheets is still not clear. The present study aims to clarify the texture evolution of the ARB processed Ti, Al, and Nb sheets. The microtexture development of niobium is discussed in the current paper, and the texture changes in Ti and Al will be addressed in future works.
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EXPERIMENTAL
Elemental foils of titanium, aluminum, and niobium were employed for the ARB process in the current investigation of microtexture development. The chemical compositions of the foils are shown in Tables I, II, III. Foils with dimensions of 2 9 3 inch were cut fr
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