Symposium L: Interaction of Phase and Defect Microstructures in Metallic Alloys, MRS Fall Meeting, Boston, December 1998

Luke S.-J. Peng and Gary S. Collins, Dept of Physics, Washington State University, Pullman, WA, USA.

Mössbauer, x-ray, and XPS measurements were made on FeRh after quenching a 53 at.% Fe ferromagnetic alloy with B2 structure into water from 800, 900, 1000, 1100, and 1200 C. Hyperfine fields were used to identify the B2 ferromagnetic phase (F), stable in the range 53-52 at.% Fe, a B2 antiferromagnetic phase (AF), stable in the range 52-50 at.% Fe, a Rh-rich fcc terminal solid solution containing about 30 at.% Fe, and magnetite (Fe₃ O₄) and wüstite (FeO). The terminal solubility of the fcc phase was determined as a function of quenching temperature from an analysis of all Mössbauer spectral areas. The F-phase dominates after quenching from 800 C, but is progressively replaced by the AF-phase, fcc phase and oxides with increasing quenching temperature. These phase changes are attributed to oxidation of Fe out of the B2 phase that leaves a more Rh-rich composition inside that transforms first to AF and then to fcc phase. While the B2 phases oxidize rapidly by quenching in water, no oxidation of the fcc phase was observed. This work was supported in part by National Science Foundation under grant DMR 96-12306 (Metals Program).