Physics of aging of nanophase alloys: Mössbauer investigation of nanocrystalline iron-copper pseudoalloy

This communication considers structural features of nanocrystals synthesized at high pressure consolidated mixed nanopowders. This system presents a pseudoalloy of mutually insoluble elements Fe and Cu, and contains pores. The study aims to demonstrate quasi-stable state of nanocrystals and factors preventing the aging. Mössbauer and X-ray analyses show a strong dependence of phase composition of Fe-Cu nanocrystalline pseudo-alloy on pressure and on aging duration. It is found pressure to coarsen phase inhomogeneity which exists initially in an as-synthesized Fe-Cu pseudoalloy. Aging duration is shown to affect the nanophase state in the same manner. It is agued that aside with typical parameters as grain size, density, phase composition of nanocrystalline substances one should know a prehistory of every sample: synthesis duration, temperature and pressure, which have a marked influence on physical properties of nanophase compacts. The Fe disorder in the Cu lattice revealed by Mössbauer spectra substantially depends on applied pressure. © 2014, Pleiades Publishing, Ltd.