Regensburg 2000 – wissenschaftliches Programm

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M: Metallphysik

M 6: Struktur und Umwandlung II

M 6.4: Vortrag

Dienstag, 28. März 2000, 11:00–11:15, H16

Effect of Ti and microstructure on the kinetics of the σ-phase formation in the Fe-Cr alloys — •Stanislaw M. Dubiel¹, Artur Blachowski¹, Jakub Cieslak¹, and Bogdan Sepiol² — ¹AGH University, Al. Mickiewicza 30, PL-30-059 Krakow — ²Universitaet Wien, Strudlhofgasse 4, A-1090 Wien

Results obtained by means of Mössbauer Spectroscopy on the

effect of Ti in a series of Ti-doped quasi-equiatomic Fe-Cr alloys

with two various microstructures will be reported. The samples

with large grains ( 385 µ m) were transformed into the σ-phase

by an isothermal annealing at 973 K and the spectra were recorded

at RT. The samples with small grains ( 31 µ m) were studied

in situ. In both cases the kinetics of transformation could be

well described in terms of the Johnson-Avrami-Mehl equation which

yielded the kinetics parameters n and k. Assuming the k-values

follow the Arrhenius law, the difference in the activation energy,

E, due to the microstructure and Ti-content was determined.

In particular it was found that the transformation: (1) was

faster in the small grain samples with the difference in E

equal to about 8 kJ/mol, and (2) was accelerated by Ti if its

concentration was less than 1.5 at%, and retarded otherwise.