Formation of amorphous states in Ti50Ni25Cu25 alloy subjected to severe plastic deformation: Nanoglass issue

Peculiarities of structure and mechanical behaviour of amorphous Ti50Ni25Cu25 alloy were the focus of this research. Amorphous melt-spun ribbons and bulk crystalline samples were subjected to high pressure torsion (HPT) in order to modify their structure and mechanical behaviour. Some properties of obtained SPD-processed samples were compared with initial state with the help of x-ray diffraction (XRD), differential scanning calorimetry (DSC) and nanohardness tests. It was shown that according to XRD no nanocrystallization occurs during HPT of melt-spun ribbons yet at the same time high density of shear bands might be formed in the alloy. Due to the formation of shear bands with the excess free volume the decrease of hardness and crystallization temperature were observed in the alloy. Analysis of structural data and mechanical behaviour allowed us to assume, that SPD processing of melt- spun Ti50Ni25Cu25 alloy might lead to the formation of structural state similar to the new kind of noncrystalline state – "nanoglass" state.