Rapid growth of FeAl intermetallic compound under high undercooling conditions

Fe-58at%Al alloy is undercooled up to 222 K (0.15TL) with the drop tube technique. It is found that there exists a critical undercooling about 185 K, beyond which a “dendrite-equiaxed” growth morphology transition occurs in FeAl intermetallic compound. This transition is characterized by sharp decrease of its grain size. Once the undercooling exceeds 215 K, the peritectic transformation is suppressed completely and a fibrous structure is formed, which results from the cooperative growth of FeAl and FeAl2 compounds.