INTERMEDIATE PHASES OF THE ALPHA-SIGMA PHASE-TRANSITION IN THE FE-CR SYSTEM

(Fe100-xCrx)100-ySny alloys with 42.0 less-than-or-equal-to x less-tha n-or-equal-to 44.7 and 0 less-than-or-equal-to y less-than-or-equal-to 5.6 were annealed at 700-degrees-C for a period of up to 1000 h in or der to cause a transformation of the alpha phase into the sigma phase. Room temperature Fe-57 Mossbauer spectra registered on the samples co nsist of a magnetic subspectrum, related to the alpha phase, and a non magnetic subspectrum, related to the sigma phase. Evidence is found th at the isomer shift of the nonmagnetic subspectrum changes continuousl y with the amount of its relative contribution in the spectrum and it reaches the value characteristic of a pure sigma phase only when its c ontribution in the two-phase sample is larger than about 30%.