Recrytallization Kinetics of a Nitrided Iron Alloy

Tez Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Metalurji Ve Malzeme Mühendisliği Bölümü, Türkiye

Tez Danışmanı: Prof. Dr. Ö.Ertuğrul Atasoy

Tezin Onay Tarihi: 1984

Tezin Dili: İngilizce

Özet:

High temperature annealing of cold worked and nitrided iron alloy containing 1%V is studied in the temperature range of 795-880 C in the hydrogen atmosphere. The results of recrystallization kinetics indicate that transformtion obeys the Avrami equation., where the time exponent, n is independent to temperature changes.. After the superimposition of both kinetics of recrystallization and VN precipitate coarsening at 860 C, it is deduced that at first, plate-like VN precipitates on sub-boundaries grow slowly with surface reaction controlled coarsening and retards the onset of recrystallization up to a critical inter-particle spacing. However afterthat, the coarsening rate turns out to be diffusion controlled. Temperature dependence of the rate of recrystallization is in the from of an Arhenius relation and satisfies the initial slow growth rate of VN precipitates on sub-boundaries. Optical microscopy is used to determine the time-temperature relation of recrystallization, and Trasnmission Electron Microscopy is used to study the precipitate morphologies with mcro-structural changes at 860 C annealing.