On the B2 → fcc transformation of Fe-Rh during deformation

It has been previously reported that deformation of the Fe-Rh intermetallic with B2-type ordered bce structure results in a B2-to-fcc phase transformation and that the Fee phase exhibits a low-temperature magnetic behaviour typical of a spin glass or a cluster glass. Using transmission electron microscopy in conjunction with X-ray diffraction, Mossbauer spectroscopy and other previously published data, we show that the B2-to-fcc transformation occurs before grain refinement and deformation-induced nanocrystallization is completed anti long before the low-temperature magnetic properties show spin-glass-like behaviour. Not only is a B2-to-bcc solid-solution transformation not observed but evidence is found for localized transformations from the B2 phase to ordered fct L1(0), and it is concluded that the metastable fee phase must contain strong chemical short-range order (CSRO), which then is progressively reduced by continued deformation in this case by ball milling. The continued reduction in the degree of CSRO is related to the development of the spin-glass-like behaviour observed after long milling times.