Analysis of an aluminum single crystal with unstable initial orientation (001) [110] in channel die compression
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INTRODUCTION
SINGLE crystals of aluminum and copper with the initial orientation (001) [110] are known to be unstable during rolling. [1-6J At large reductions, the crystal orientation splits and evolves into the two complementary copper components, (112) [III] and (II2) [111]. Some researchers also found the Goss component «(110) rOOl]) in copper crystals,[UJ while others did notYJ In studies of aluminum crystals, however, only the two copper components were observed. [4,6J In the analysis of this unstable behavior, the overall deformation is often approximated by homogeneous plane strain compression. In order to assess the validity of these assumptions, the rolling conditions must be known. The publications by Verbraak,nJ Hinkel et al.pl and Szymanski and Karp[4J did not provide sufficient information to calculate the ratio of contact length to average thickness, I/h, or the ratio of the contact length to width, l/w. These are needed to estimate the degree of inhomogeneity of the deformation and the lateral spread. Bauer et alY] provided the necessary information for calculation of I/h, but the conditions for homogeneous plane strain deformation were not met. The deformation in the experiments of Kohlhoff et al. [5J was approximately homogeneous plane strain compression. In addition, a description of the evolution of the rolling texture and the structure was provided. They showed that at moderate strains, spreading of the initial orientation occurred by rotations about the transverse direction. The structure consisted of large regions with gradual changes in orientation. With increasing strain, the rotation around the transverse direction continued, and two distinct groups of differently oriented regions developed. The transition regions were observed to de-
R. BECKER, Staff Engineer, and L.A. LALLI, Division Manager, are with the Fabricating Technology Division, Alcoa Laboratories, Alcoa Center, PA 15069. J.F. BUTLER, Jr., previously at the University of Pittsburgh, is Senior Research Engineer, Light Product Division-Research, United States Steel Technical Center, Monroeville, PA 15146. H. HU, Research Professor, is with the Department of Material Science and Engineering, University of Pittsburgh, Pittsburgh, PA 15261.
Manuscript submitted March 1, 1990. METALLURGICAL TRANSACTIONS A
crease in volume fraction until the boundaries between regions of stable orientation appeared as sharp transition bands in the optical microscope. At large strains, the two copper components and the Goss component were observed. Kohlhoff et al.[5] plotted the lattice rotation about the transverse direction as a function of strain to illustrate the evolution of the lattice orientation. Their results showed that above a strain of e = 1,0, the rate of lattice rotation with increasing strain decreased as the stable copper orientation was approached. In this study, the details of the evolution of the microstructure are presented for an aluminum single crystal with initial orientation (001) [110] deformed in plane strain compressio
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