Two-phase coexistence in Fe–Cu alloys synthesized by ball milling

Mechanical alloying with a Spex 8000 mixer/mill operated at two intensities was used to synthesize a series of Fe 100− x Cu x alloys with Cu concentrations from x=0 to x=49. X-ray diffractometry was used to measure the volume fractions of the b.c.c. and f.c.c. phases in the alloys. Mössbauer spectrometry was used to determine Cu concentrations in the b.c.c. phase, and identify inhomogeneities in Cu concentration in the b.c.c. phase. With higher milling intensity, there was a narrowing of the range of compositions for f.c.c. plus b.c.c. coexistence, and a shift towards Fe-rich compositions. The composition range of two-phase coexistence is understood in terms of heterogeneities in both defect density and concentration.