Discontinuous coarsening of lamellar cellular precipitate in an austenitic Fe-30 wt.%Ni-6 wt.%Ti alloy—II. Growth kinetics
✍ Scribed by R.A. Fournelle
- Publisher
- Elsevier Science
- Year
- 1979
- Weight
- 847 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0001-6160
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✦ Synopsis
The growth kinetics of discontinuous coarsening of lamellar cellular precipitate in an austenitic Fe-30 wt.p;Ni-6 wt.f,Ti Alloy aged at temperatures ranging from 400 to 900°C have been studied by light and electron microscopy measurements of cell growth rate and lamellar spacing. Analysis of the growth kinetics shows that the Livingston-Cahn [l] model is not obeyed with the reason being that not all of the available volume free energy is used in the first reaction. A theory which considers the volume free energy remaining after the first reaction is presented. According to this theory, the growth rate of the coarsening reaction in this system is controlled by grain boundary diffusivity, f&. and depends on the growth rate, Vt, and lamellar spacing, i t, of the first cellular precipitation reaction according to the following equation: vr= "Ii:+ j.f $$(A&+?).
R&urn&-Nous avons &die la cinetique de croissance discontinue de prtcipitb lamellaires cellulaires dans un alliage Fe-30y0Ni-6YGTi vieilli entre 400 et 900°C. en mesurant par microscopies optique et ilectronique la vitesse de croisaance des cellules et I'espacement des lamelles. L'analyse de la cinetique de croissance montre qu'elle n'oMit pas au modtle de Livingston et Cahn [l]; la raison en eat que toute l'energie libre volumique disponible nest pas utilisee dans la premiere reaction. Nous prtsentons une thtorie qui tient compte de I'energie libre volumique restant apres la premiere reaction. Selon cette thborie. la vitesse de la reaction de croissance dans ce systeme est contrblee par la diffusivite Db aux joints de grains, et elle depend de la vitesse de croissance V, et de I'espacement A, des lamelies de la premiere reaction cellulaire selon l'equation suivante: