PHASE-DIAGRAM, SUPERLATTICES AND ANTIPHASE DOMAINS OF FE3ALX, S-THAN-OR-EQUAL-TO-X-GREATER-THAN-OR-EQUAL-TO-1.3, INVESTIGATED BY NEUTRON-SCATTERING

The states of order of iron-aluminium-alloys with compositions around Fe3Al have been investigated by neutron scattering. The results lead t o the following description of their structures: (i) These alloys have the long-range ordered DO3 structure up to the following temperatures : Fe-0.2Al up to at least 873 K, Fe-0.25Al and Fe-0.3Al up to about 10 50 K, atomic fractions of Al are quoted. (ii) Some phase boundaries sh own in the current Fe-Al phase diagram turned out to be no phase bound aries at all, but to have bearing only on the size of antiphase domain s. There are critical temperatures above which antiphase domain bounda ries are in thermodynamic equilibrium. The present results suggest rev isions of the current Fe-Al phase diagram.