Degradation of plastic properties after electrocharging in 1 N H 2 SO 4
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Interdiffusion Coefficient (/) • 1012) m2/s Serial Number 1.
2. 3.
Temperature (K) 873 923 977
Heumann
Wagner
Cu4Zr
CuZr 2
Cu4Zr
CuZr 2
0.06 0.093 0.18
0.007 0.024 0.045
0.058 0.07 0.26
0.008 0.012 0.03
CuZr 2
could be attributed to constraints for nucleation and growth processes occurring in the diffusion zone. I71 However, the exact quantifications of free-energy changes associated with the formation of intermetallic compounds are complex because of several nonequilibrium processes occurring in the diffusion zones, t8] The exact mechanism of the growth of a phase with incubation period is not well understood; [9] however, Philibert tT] mentions that the growth of the phase is not only controlled by its critical thickness value as imposed by nucleation criteria but also depends on the magnitude of diffusivity at adjacent phases. The present investigation indicates that CuZr2 forms first with an incubation period of 1.03 hours, then followed by Cu4Zr, with an incubation time of 1.07 hours. The parabolic growth of these phases suggests that layer growth is essentially through volume diffusion-controlled process.
The authors wish to thank Dr. S. Banerjee and Dr. P. Mukhopadhyay for useful discussions and Mr. P.S. Gawde for assistance in experimental work. REFERENCES 1. H. Kimura, Y. Minobe, S. Uehera, K. Honma, and N.K. Gakkalshi: J. Jpn. Inst. Met., 1973, vol. 37 (5), pp. 552-55. 2. K. Bhanumurthy: Ph.D. (Physics), Bombay University, India, 199l. 3. K. Bhanumurthy, G.B. Kale, S.K. Khera, and M.K. Asundi: Metall. Trans. A, 1990, vol. 21 (11), pp. 2897-2903. 4. K. Bhanumurthy, G.B. Kale, and S.K. Khera: J. Nucl. Mater., 1991, vol. 185, pp. 208-13. 5. G.B. Kale, S.K. Khera, and R.V. Patih Mater. Sci. Forum, 1985, vol. 3, pp. 319-24. 6. E. Kneller, Y. Khan, and U. Gorres: Z. Metallkd., 1986, vol. Bd (77), pp. 43-48. 7. J. Philibert: Defect and Diffusion Forum, 1989, vol. 66-69, pp. 995-1014. 8. A.J. Hickl and R.W. Heckel: Metall. Trans. A, 1975, vol. 6A, pp. 431-40. 9. K. Hirano and Y. Iijima: in Diffusion in Solids: Recent Developments, M.A. Dayananda and G.E. Murch, eds., AIME, Detroit, MI, Sept. 17, 1984, p. 141.
E ~C'~
0
-A
I00
10.5
I10
104/
T
11.5
(K)
Fig. 5 --Temperature dependence of diffusion coefficients for Cu4Zr and CuZr2.
Degradation of Plastic Properties after Electrocharging in 1 N H2S04 /)(CuZr2) = 3.12 • 10 -7 9exp - ( ( 1 2 5 . 0 -+ 22.1 (kJ/mole))/RT) m2/s
[2] where T is the temperature of annealing and R is expressed in kJ/mole, K. Diffusion reaction between two metals, in principle, should lead to the formation of all compounds, as depicted in equilibrium phase diagram. [5] The zirconiumcopper phase diagram indicates [6] several intermetallic compounds, namely, Cu51Zrl4, (Cu4Zr) Cu23Z~13, CuloZr7, CuZr, CusZrs, and CuZr2. The present study confirms the formation of only Cu4Zr and CuZr2 in the diffusion zone with incubation periods. The absence of other phases METALLURGICAL TRANSACTIONS A
DONGIL KWON, SUNGHAK LEE, and ROBERT J. ASARO One of the distinct roles of hydrogen i
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