A new route to bulk nanostructured metals
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This work was conducted as part of the in-house research activities of the Processing Science Group of the Air Force Research Laboratory’s Materials and Manufacturing Directorate. The support and encouragement of the laboratory management and the Air Force Office of Scientific Research (Dr. C.S. Hartley, Program Manager) are gratefully acknowledged. Two of the authors (JB and TB) were supported under the auspices of Air Force Contract No. F33615-96-C-5251, and two others (DPD and TRB) were supported through Air Force Contract No. F33615-94-C-5804. REFERENCES
(b)
(c)
(d ) Fig. 5—Macrographs of Ti-6Al-4V samples preheated at 970 ⬚C and subjected to a single ECAE pass. Upset prestrains prior to shear deformation were (a) 0.038, (b) 0.14, (c) 0.28, and (d ) 0.44.
flow softening when the strain path is changed after only a small prestrain of the order of 0.10. On the other hand, the results in Figures 1 and 2 reveal that prestrains of the order of 0.20 to 0.40 significantly reduce or essentially eliminate the majority of the flow-softening behavior over intervals of strain comparable to those imposed during one pass through an ECAE die with a 90 deg angle (i.e., a strain of ⬃ 1.0). Although the changes in strain paths were different in the two cases examined here (plane strain rolling → uniaxial upset vs uniaxial upset → simple shear), it is likely that similar effects and interpretations would pertain for other strain-path changes. Indirect support for this conclusion may be obtained from the work of Korshunov et al.,[10] who found similar kinetics of dynamic globularization for a variety of deformations involving markedly different types of strain path changes. METALLURGICAL AND MATERIALS TRANSACTIONS A
1. S.L. Semiatin, V. Seetharaman, and I. Weiss: in Advances in the Science and Technology of Titanium Alloy Processing, I. Weiss, R. Srinivasan, P.J. Bania, D. Eylon, and S.L. Semiatin, eds., TMS, Warrendale, PA, 1997, pp. 3-73. 2. D.P. DeLo, T.R. Bieler, and S.L. Semiatin: in Ultrafine Grained Materials, R.S. Mishra, S.L. Semiatin, C. Suryanarayana, N.N. Thadhani, and T.C. Lowe, eds., TMS, Warrendale, PA, 2000, pp. 257-66. 3. D.P. DeLo and S.L. Semiatin: Metall. Mater. Trans. A, 1999, vol. 30A, pp. 2473-81. 4. S.L. Semiatin and G.D. Lahoti: Metall. Trans. A, 1981, vol. 12A, pp. 1705-17. 5. S.L. Semiatin, J.C. Soper, and R. Shivpuri: Metall. Mater. Trans. A, 1994, vol. 25A, pp. 1681-92. 6. S.I. Oh, S.L. Semiatin, and J.J. Jonas: Metall. Trans. A, 1992, vol. 23A, pp. 963-75. 7. V.M. Segal, R.E. Goforth, and K.T. Hartwig: U.S. Patent 5,400,633, 1995. 8. S.L. Semiatin and T.R. Bieler: Metall. Mater. Trans. A, 2001, vol. 32A, in press. 9. I. Weiss, G.E. Welsch, F.H. Froes, and D. Eylon: in Titanium: Science and Technology, G. Luetjering and W. Bunk, eds., Deutsche Gesellschaft fur Metallkunde e.v., Oberursel, Germany, 1985, pp. 1503-10. 10. A.A. Korshunov, F.U. Enikeev, M.I. Mazurskii, G.A. Salishchev, A.V. Muravlev, P.V. Chistyakov, and O.O. Dimitriev: Russ. Metall., 1994, vol. 3, pp. 103-08.
A New Route To Bulk Nan
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