Coarsening kinetics of lamellar microstructures: Experiments and simulations on a fully-lamellar Fe-Al in situ composite
X. Li, F. Bottler, R. Spatschek, A. Schmitt, M. Heilmaier, F. Stein,
Volume: 127. Pages: 230--243
DOI: 10.1016/j.actamat.2017.01.041
Published: 2017
Abstract
Abstract A very fine lamellar microstructure consisting of the intermetallic
phases FeAl and FeAl2 forms in binary Fe-Al alloys due to the eutectoid
reaction Fe5Al8 ↔ FeAl + FeAl2, which takes place in the Al range
between 56.0 and 64.4 at.% at 1095 °C. A fully lamellar microstructure
is obtained at the eutectoid composition 60.9 at.% Al. The initial
lamellar spacing λ 0 of as-cast material is 200 ± 40 nm. In this
study, the kinetics of coarsening of the FeAl + FeAl2 lamellar microstructure
is investigated at four different temperatures in the range 600 °C–1000 °C
with holding times from 10 min to 7000 h. It is found that the increase
of the lamellar spacing can be described as λ 3 = λ 0 3 + k t . The
value obtained for the activation energy proves that the lamellar
coarsening is a volume-diffusion-controlled process. Besides the
experimental investigations, phase-field modeling is used to simulate
the lamellar coarsening. The results are in good agreement with the
experimental observations with regard to the evolution of the lamellar
morphology and the value of the coarsening exponent.