PRELIMINARY-STUDY ON ALUMINUM-BASED NANOPHASE COMPOSITES AL88NI10Y2 AND AL88NI8Y4

A new kind of aluminium-based alloy, part amorphous/part crystalline, can be produced directly by rapid quenching of the liquid. These mater ials have a novel structure of nanometer-sized crystals in an amorphou s matrix and quite remarkable mechanical properties. The materials can be considered to be nanoplase compsites. In this work Al88Ni10Y2 and Al88Ni8Y4 (at pct) nanophase composites consisting of a nanoscale disp ersion of fcc-Al crystallites uniformly dispersed in an amorphous matr ix, have been produced by melt-spinning. They have much higher microha rdness HV than fully amorphous alloys with the same composition, while retaining good bending ductility The volume fraction, crystallite siz e and distribution of the fee-Al phase have been estimated by DSC, X-r ay diffraction and TEM. It is found that the microstructure and proper ties of the nanophase composites are very sensitive to the composition and the quenching conditions. Increasing the Y content and decreasing the Ni content at a given Al content gives much smaller dispersed nan ophase aluminium crystallites. The volume fraction and crystallite siz e of the fee-Al phase increase with a decrease of wheel speed (quenchi ng rate). The effects of Y and Ni contents on the ease of formation of the nanophase composites are discussed. The origins of the novel mech anical properties are also considered.