SAXS study on the structure and crystallization of amorphous metallic alloys

Abstract

The change in structure of several amorphous alloys as Fe-P-C, Fe-B and Pd-Au-Si alloys during isothermal ageing was examined using small angle X-ray scattering technique as well as transmission electron microscopy. The SAXS intensity was related to two different types of scattering sources depending on ageing period and temperature. As-splatted amorphous alloys and the specimens aged for short period at relatively low temperature, where specimens remained in amorphous state, showed a weak and spreaded SAXS intensity. This indicates an existence of electron density fluctuation in amorphous phase. The dimension of their scattering regions was estimated to be 1.8 to 2.4 nm for Fe-P-C alloys, and 1.2 to 0.8 rim. for Fe-B alloys, respectively, by analysing the electron density-density correlation function derived from observed SAXS intensity. The origin has been discussed based on one dimensional model. A compositional fluctuation was made clear to occur in fine scale of about 1 nm in amorphous Fe-B and Fe-P-C alloys. When the alloys were aged for longer period below their crystallization temperatures, fine crystalline particles precipitate; those are a two phase lamella structure of Fe3P andα-Fe for a Fe83P10C7 alloy, an Ferich single phase for Fe83B17 alloy, and a Pd-rich single phase for Pd76Au6Si188 alloy, respectively. Their size and structure were determined from the analysis of SAXS data and TEM observation.