Effect of copper content on structure and phase transformations in melt-spin TiNi - TiCu alloys
The thin ribbons 30 - 50 μm thick of the Ti50Ni50 - x Cu x ( x = 25; 26; 28; 30; 32;3 4; 36; 38 at. %) alloy were produced by the melt- spinning technique at a cooling rate of approximately 106K/s. It has been revealed that at the content of copper 25 and 26 at.% alloys are in the amorphous-crystalline state, while at the content of copper above 26 at.% alloys are in the amorphous state. It has been shown, that isothermal crystallization of alloys with the copper content from 25 to 32 at.% leads to formation of single- phase structure of B2, which when cooling transforming into the martensite phase B19.Noticeable decrease in characteristic temperatures of martensitic transformation at increase in content of copper is revealed. In alloys with the content of copper more than 32 ат. the % after crystallization two-phase structure of B2+B11 is formed, at the same time B11-phase (TiCu) substantially prevents B19↔B2 transformation in the alloy with 34 at.% copper, and in the alloys with 36 and 38 at.% copper blocks all structural transformations.