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| FATIGUE CRACK GROWTH FOR Ti-6Al-4V ALLOY IN WATER |
| by GAO Shujun; QIN Rongshi; ZHANG Suisheng; WAN Xiaojing (Institute of Metal Research. Academia Sinica. Shenyang) |
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Cite this article:
by GAO Shujun; QIN Rongshi; ZHANG Suisheng; WAN Xiaojing (Institute of Metal Research. Academia Sinica. Shenyang). FATIGUE CRACK GROWTH FOR Ti-6Al-4V ALLOY IN WATER. Acta Metall Sin, 1986, 22(3): 15-145.
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Abstract The environmentally assisted fatigue crack growth for annealed Ti-6Al-4V alloy plates in distilled water has been studied by using fracture mechanics method. Fatigue crack growth rates da/dN were determined as a function of stress intensity factor range AK from 20 to 45 MPam~(1/2), temperature from 273 to 353K and frequency from 0.1 to 75 Hz at a load ratio of 0.11. Reference data were obtained in laboratory air at room temperature and a frequency of 10 Hz. Futhermore, SEM fractographic studies have been carried out to observe the fatigue fracture morphologies. The experimental results showed that fatigue crack growth in water is enhanced as compared with that in air. The relationship between da/dN and △K follows the Paris equation. Fatigue crack growth rates were found to decrease with increasing temperature and to increase with decreasing frequency. The temperature dependence of crack growth rate at a frequency of 10 Hz can be described as:da/dN=Ae~(Q/RT)(△K)~(2.7), where Q=6.2 kJ/mol. Fatigue fracture surface is composed of relatively flat regions and irregular fracture regions. The flat regions are covered with three kinds of fatiguestriations: ductile striations, fissure striations and brittle striations. The irregular fracture regions are heavy plastic deformation areas, combined sometimes with small areas of striations. The ductile and fissure striations show an approximate one to one correspondence with the load cycles, whereas the spacing of the brittle striations is several times larger than the corresponding macroscopic growth rate. Enhancement of fatigue crack growth by water is believed to result from embrittlement by hydrogen that is produced by the reaction of water with the crack surface of Ti alloy. The observed temperature and frequency effects on fatigue crack growth rate can be explained in terms of a strain-induced hydride mechanism. Formation of strain-induced hydride is considered to be the rate-controlling process for crack growth.
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Received: 18 March 1986
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1 Gao, S. J. (高树浚); Simmons, G.W.; Wei, R.P., Mater. Sci. Eng., 62 (1984) , 65．
2 Bowen, A.W., Acta Metall., 23 (1975) , 1401．
3 Ward-Close, C.M.; Beevers, C.J., Metall. Trans., A, 11A (1980) , 1007．
4 Evans, W.J.; Gostelow, C.R., Metall. Trans., A, 10A (1979) , 1837．
5 Boyd, J.D., The Science, Technology and Application of Titanium, Eds. Jaffe, R.I.; Promiscl, N.E., Pergamon Press, London, 1970, p. 545．
6 Hall, I.W.; Hammond, C., Mater. Sci. Eng., 32 (1978) , 241．
7 Allen, R.P.; Taggart, R.; Polonis, D.H., Acta Metall., 14 (1966) , 741．
8 Hall, I.W., Scand. J. Metall., 7 (1978) , 187．
9 Boyer, R.R.; Spurr, W.F., Metall. Trans., A, 9A (1978) , 23．
10 Pao, P.S.; Lederich, R.J.; Sastry, S.M.L., Micro and Macro Mechanics of Crack Growth, Eds. Sadananda, K.; Rath, B.B.; Michel, D.J., TMS-AIME, 1982, p. 71． |
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