16. Lindner R., Karnik F. “Diffusion of Radioactive Cop- perIin Technical Steel” Acta Metallurgica, vol. 3, is- sue3) pp 297 (1955).
17. Gertsriken S.D., Dekhtyar I.Ya., Solid State Diffusion in Metals and Alloys, United States Atomic Research Commission, State Publication House for Physicalm- Mathematical Literature, Moscow, p. 482 (1960).
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Reactions, Springer Press Publication, Berlin, pp. 55 (1955).
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20. Laik A., Gawde P.S., Bhanumurthy K.. “Characteris- tics of Interdiffusion Between H17-4 PHsSteel and- Nickel”, Metallurgical and Materials Transactions A, vol. 3A no. 4, pp. 733-741 (2008).
Technical Review and Discussion
Microstructure and Properties of Nb, V and N Modified CB7Cu-l (17-4 PH) Steel A. Murthy, S. Lekakh, V. Richards and D. Van Aken Missouri University of Science and Technology, Rolla, MO, USA
Reviewers: The estimated homogenization times were ap- proximately two hours and one hour for 1200°C (2190°F) and 1250°C (2280°F), respectively. Experiments were con- ducted at 1200°C (2190°F) for one hour and two hours, as well as 1250°C (2280°F) for one hour. All specimens were air-cooled after homogenization. The sentences seem to con- tradict each other. Can you clarify?
Authors: We weren’t confident of the calculation which is an estimate based on approximate dendrite arm spac- ing and diffusivities that are only known with confidence to plus or minus a facto of three times. Therefore this was sort of experimental [estimates]. Subsequent analy- sis addresses the success of the homogenization. The
estimation for homogenization: 1200C, 2h and 1250C, 1h was based on the first principles using approximate dendrite arm spacing and hence the confidence level of estimation was low. We included 1200C, 1h in our ex- periments so that we could observe if there is any im- provement in homogenization between 1200C, 1h and 1200C, 2h samples.
An indicator of better homogenization (especially Cr seg- regation) in 1200C, 2h samples as compared to 1200C,1h was the lower amount of retained austenite after austenite conditioning and cooling . This may indicate that the reten- tion of austenite was related to the degree of homogeniza- tion and that one hour at 1200°C is insufficient to produce an adequate redistribution of the alloying elements which could have raised the Ms temperature and caused an in- crease in the retained austenite.
To summarize, 1200C, 1h experiment was used to study how the homogenization process proceeded and also to check if the theoretical estimation was real and whether 2 hours at 1200C made any difference as compared to 1h.
International Journal of Metalcasting/Spring 10
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