PHASE-TRANSITION IN AN FE-23.2AL-4.1NI ALLOY

Abstract

The phase transition in an Fe-23.2 at. pct Al-4.1 at. pct Ni alloy has been investigated by means of transmission electron microscopy. In the as-quenched condition, the microstructure of the alloy is a mixture of (A2 + B2) phases. When the as-quenched alloy is aged at temperatures ranging from 500-degrees-C to 1050-degrees-C, the phase transition sequence is found to be (A2 + B2*) --> (B2 + B2*) --> B2 --> A2, where B2* is also a B2-type phase. It is worthwhile to note that the coexistence of two kinds of ordered B2 phase has not previously been observed by other workers in the Fe-Al-Ni ternary alloy system.