Sezonenko A. Structure and functional properties of multicomponent NiTi-based alloys in melt-spun form

The two series of multicomponent alloys (Ti32Hf18)Ni(50-х)Сuх and (Ti,Hf,Zr)А[(Ni,Со)25(Cu,Ag)25]В were produced by planar flow rapid solidification technique in ribbons form. Variation of different alloying elements and there concentration around base alloys TiNiСu was resulted in formation the different initial structural state (totally amorphous structure, mixture of the amorphous and crystalline phases) in ribbons. The material structure was examined by the X-ray diffraction, transmission and scanning electron microscopy; the thermodynamic properties were studied by differential scanning calorimetry; the mechanical and functional (shape memory/superelasticity) properties were studied in tension at room temperature (~25°C) and also for tests on heating from room temperature up to 700°C. The main results of this manuscript are: Thermal stability of the amorphous phase in (Ti32Hf18)Ni(50-х)Сuх, (Ti,Hf,Zr)50[(Ni,Со)25(Cu,Ag)25]50 and (Ti,Hf,Zr)55[(Ni,Со)25(Cu,Ag)25]45 ribbons with martensite transformation after crystallisation was determined by two characteristic temperatures: glass transition Tg and crystallisation Tx temperatures. The "dynamic constant load" method was developed for visualise the superplasticity effect near Tg temperature for amorphous and amorphous-crystalline melt-spun ribbons. (Ti32Hf18)Ni(50-х)Сuх, (Ti,Hf,Zr)50[(Ni,Со)25(Cu,Ag)25]50 and (Ti,Hf,Zr)55[(Ni,Со)25(Cu,Ag)25]45 ribbons exhibit the superplasticity effect near Tg temperature, value of maximum deformation reaches 60-70%.