A study of the improvement
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XINGGANG JIANG, QINGLING WU, JIANZHONG CUI, and LONGXIANG MA
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In(el) Fig. 6--Weibull plot of the fracture strain of differently treated NiAI specimens. P; is the probability for the fracture strain to be below a certain value. The details of the specimen preparation are listed in Table I.
fracture stresses are in the upper range of those commonly found for engineering ceramics. The loss in ductility due to grinding is recovered to a large extent by annealing. ACKNOWLEDGMENTS
This research was sponsored by the Division of Materials Sciences, Office of Basic Energy Sciences, United States Department of Energy, under contract No. DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc. The authors thank M.K. Ferber and E.P. George for discussions and K. Spence for editing. REFERENCES 1. R.D. Noebe, R.R. Bowman, and M.V. Nathal: Int. Mater. Rev., in press. 2. R.R. Bowman, R.D. Noebe, S.V. Raj, and I.E. Locci: Metall. Trans. A, 1992, vol. 23A, pp. 1493-1508. 3. J.H. Schneibel, M.G. Jenkins, and P.J. Maziasz: HighTemperature Ordered lntermetallic Alloys V, Materials Research Society Symposia Proceedings, 1. Baker, R. Darolia, J.D. Whittenberger, and M.H. Yoo, eds., Materials Research Society, Pittsburgh, PA, 1993, vol. 288, pp. 549-54. 4. C.A. Johnson: Report No. 79CRD212, General Electric Co., Schenectady, NY, December, 1979. 5. G. Quinn: J. Am. Ceram. Soc., 1990, vol. 73, pp. 2374-84. 6. E.M. Schulson and J.A. Roy: Acta Metall., 1978, w)l. 29, pp. 29-38. 7. K. Vedula, K.H. Hahn, and B. Boulogne: High-Temperature Ordered Intermetallic Alloys 111, Materials Research Society Symposia Proceedings, C.T. Liu, A.I. Taub, N.S. Stoloff, and C.C. Koch, eds., Materials Research Society, Pittsburgh, PA, 1989, vol. 133, pp. 299-304. 8. R.W. Margevicius and J.J. Lewandowski: Scro~ta Metall. Mater., 1991, vol. 25, pp. 2017-22. 9. R.D. Noebe, C.L. Culler, and R.R. Bowman: J. Mater. Res., 1992, vol. 7, pp. 605-12. 10. E.P. George and C.T. Liu: J. Mater. Res., 1990, vol. 5, pp. 754-62. I1. 1. Baker, P, Nagpal, F. Liu, and P.R. Munroe: Acta Metall. Mater., 1991, vol. 39, pp. 1637-44. 2596--VOLUME 24A, NOVEMBER 1993
In recent years, various thermomechanical processes (TMP) have been developed to produce a fine grain size in high-strength aluminum alloys.ll-6I Paton eta/. 171 have applied their TMP method and processed 7075 and 7475 aluminum alloys. These materials exhibited optimum superplastic behavior at a temperature 789 K (516 ~ and a strain rate of 2 x l 0 -4 s - I . However, Bampton and Edington ISI reported that because the high-strength 7075 aluminum alloy contains more Fe and Si impurities than the 7475 aluminum alloy, its maximum elongation is lower than that of 1200
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