STRUCTURAL AND MOSSBAUER STUDIES OF FE1-XALX ALLOYS OVER THE ENTIRE COMPOSITION RANGE

Metastable Fe1-xAlx alloys over the entire composition range have been investigated by X-ray diffraction and Mossbauer effect measurements. Alloys with x less than 0.55 are bcc, whereas those with x > 0.9 are fcc, in between, the samples are amorphous. The Mossbauer spectra at 300 K for the bcc alloys with x < 0.5 consist of a broadened sextet and the spectra for the alloys with x greater-than-or-equal-to 0.5 are quadrupole-split doublets with a slight asymmetry. The magnetic hyperfine field at 4.2 K decreases monotonically with Al concentration from 340 kOe in pure Fe to zero at x = 0.7. The isomer shift increases essentially linearly with Al concentration, and reaches a maximum at x almost-equal-to 5. It is noted that at the boundary of x almost-equal-to 0.55 separating the bcc and the amorphous states, there is no discernible change in either hyperfine field or isomer shift.