X-ray analysis of microstructure in Au-Fe melt spun alloys

Supersaturated Au80Fe20 and Au70Fe30 solid solutions have been obtained by rapid solidification. The lattice constant a0 of the as-quenched FCC phase was of 4.025 and 3.989 A for Au80Fe20 and Au70Fe30, respectively. Thermal treatments have been performed in the temperature range between 320 deg. C and 550 deg. C. A precipitation reaction has been observed in Au80Fe20 only after prolonged annealing at low temperature (320 deg. C/168 h). In Au70Fe30 an increase in the lattice constant has been observed after thermal treatments, giving values ranging from 3.998 to 4.044 A. Precipitation occurs at grain boundaries and into grains. Low-temperature annealings give lamellar precipitates, which grow and transform into globules at higher temperatures. A Williamson-Hall plot for the FCC phase shows a significant scatter due to occurrence of planar defects. A detailed analysis of microstructure have been obtained by Rietveld analysis of peak broadening. Precipitation reaction leaves a Fe-depleted matrix, which shows a cristallite size of about 200 A and an r.m.s. microstrain of 6x10-3. Compound fault probability has been estimated from asymmetric peak profile