SYNTHESIS OF POROSITY-FREE NANOCRYSTALLINE MATERIALS WITH ULTRAFINE GRAIN-SIZE BY ANNEALING AMORPHOUS ALLOY UNDER HIGH-PRESSURE

A porosity-free nanocrystalline Fe735CulNb3Si135B9 alloy with an ultra fine grain size of 4-6 nm has been synthesized. Experiments were carri ed out by annealing amorphous Fe735CulNb3Si135B9 alloy at a temperatur e of 823 K under a pressure of 5 GPa in a belt-type pressure apparatus . The microstructure of the samples annealed respectively under high p ressure and normal pressure was investigated using X-ray diffraction ( XRD), electron diffraction (ED) and transmission electron microscopy ( TEM). Analysis results show that the high pressure makes the size of c rystalline phase become much smaller,from 10-12 nm for the normal pres sure to 4-6 nm for 5 GPa, without changing the lattice type of the cry stalline phase, which is attributed to the effects of pressure on the crystallization process of amorphous alloy. (C) 1998 Acta Metallurgica Inc.