HRTEM studies of amorphous ZrNiTiCu nanocrystalline composites

Abstract

Ball milling of easy glass forming Ti(25)Zr(17)Ni(29)Cu(29) alloys lead to the formation of an amorphous structure accompanied by a substantial increase of powder microhardness. The powders show clear glass transition effect and a few stage crystallization starting above 500 degrees C. High-resolution transmission electron microscope technique allowed identifying nanocrystalline inclusions as Cu(12)NiTi(7) within the amorphous powder. The amorphous powders mixed with nanocrystalline iron or silver powders were hot pressed to form composites. A narrow 200 nm broad intermediate single-phase layer at the amorphous-phase/iron interface containing all elements present in the composite was identified using transmission electron microscope and high-angle annular dark field detector techniques. scanning transmission electron microscopy energy dispersive spectroscopy line profile showed gradual change of composition within the intermediate zone. Amorphous phase contains small nanocrystals of size close to 10 nm identified using High-resolution transmission electron microscope as Cu(12)NiTi(7.) Compression tests have shown better plasticity of composites than in the case of pure hot-pressed amorphous powder; furthermore, high elastic limit of composites and the ultimate compression stress of about 1800 MPa for composites containing 20% Fe and near 700 MPa for those with 20% Ag.