Investigations of Glassy and Nanostructured Metal-Metal Type Alloys

Glassy, bulk glassy, nanostructured alloys and the composites obtained from them possess unique mechanical properties, high corrosion resistance and are promising candidates to be applied in tools, elastic, sportive and structural materials. In addition, the formation of an icosahedral quasicrystalline phase has been observed in many but not all of the bulk glass formers. We present new results and also summarize a large number of earlier results obtained by our research group for various (Zr/Hf)-Ti-Ni-Cu with minor additions of noble metals. The emphasis is on bulk glass formers and the nanostructured alloys produced upon the devitrification of glassy alloys or directly upon solidification. The purpose is to describe and emphasize their most common features and properties as well as to show the future prospects of the field. Attention is also given to the new class of Cu-based bulk metallic glasses derived by enrichment in copper of conventional Zr/Hf based bulk metallic glasses. These are found to posses high yield strength of above 2 GPa, high hardness >HV 600, high elastic energy and total (plastic and elastic) elongation of 2-2.5%. New Cu-Zr-Ti-NM and Zr-Ti-Ni glassy alloys and bulk glass formers exhibiting formation of a nanoscale icosahedral phase on devitrification are also developed in the present work. The icosahedral phase in Metal-Metal type glass formers, especially Zr and Hf-based alloys is found to be formed in composition ranges close to that of the cF96 cubic Ti ₂Ni-type phase with a large unit cell size. Similarities in the structure of the icosahedral and cF96 phase as well as the reasons for the nanoicosahedral phase formation in Zr-, Ti-, Hf- and Cu-based alloys are discussed. Fine precipitates of the nanoicosahedral phase in a glassy matrix form a nanocomposite and improve the ductility of the glassy alloys.