THE PHASE-TRANSITION IN ANNEALED MECHANICALLY ALLOYED FE-CU

Using Mossbauer spectra and x-ray diffraction patterns, annealed mecha nically alloyed Fe-Cu has been investigated in this paper. It is found that in Fe0.8Cu0.2, after it has been milled, fcc-Cu has transformed into bcc-Cu, and some Cu atoms have diffused into the Fe. After the al loy has subsequently been annealed, it is found that bcc-Cu has transf ormed back into fcc-Cu, while the Cu atoms in the Fe have been separat ed. In Fe0.6Cu0.4, after being milled, an fcc-Fe-rich phase has been f ormed, and after the alloy has subsequently been annealed, this has tr ansformed back to bcc-Fe. The shorter the milling time and the higher the annealing temperature, the faster the transformation. In Fe0.5Cu0. 5, after it has been annealed, the fcc-Fe-rich phase has transformed t o bcc-Fe also, and the fcc-Cu-rich phase remains when the annealing te mperature increases. All of these results show that the fcc-Fe-rich ph ase in the milled samples is a metastable phase-it will transform to s table bcc-Fe when it is annealed-while the long-milling-product fcc-Cu -rich phase is a stable phase.