The DSC and EXAFS studies of mechanical agitation effects on the local structure of splat-cooled amorphous Ni₇₅Si₈B₁₇ alloy

Effects of mechanical agitation, extreme cold working, on the structural changes of splat-cooled amorphous alloy were investigated by the differential scanning calorimetry (DSC) and extended X-ray absorption fine structure (EXAFS) methods. The amorphous alloy composed of both matrix and Ni-enriched clusters did not have a detectable endothermic reaction. Since an amorphous alloy agitated by filing did have an endothermic reaction related to a decrease of glass transition temperature as measured by DSC, mechanical agitation has an effect on the structural relaxation and is interpreted with a proposed hierarchy diagram. The filed amorphous phase was changed by milling for 20 h into a chemically homogeneous amorphous state. Further, by milling for 100 h it eventually changed to an amorphous state such as a supercooled liquid matrix with small mean bond distance. Its glass transition temperature, T_g, was decreased to near room temperature. In this state, molecular clusters with large bone distance were separated as a precursor of metastable phase from the supercooled liquid.