Transformation Characteristics And Microstructure Of TiNi_1-xCu_x Shape Memory Alloy And Thin Film Preparation

In this paper, TiNi(i-x)Cux(X=0, 5, 10, 14, 18at.%) alloy was prepared and the transformation characteristics under different heat treatment processes and thermal cycling times were investigated systematically by differential scanning calorimeter (DSC), X-Ray Diffraction (XRD) and Transmission Electron Microscope (TEM) etc. Research of different composition alloy showed: when the content of Cu was 5at.%, two-step transformation (B2 R B19') occurred; when the content of Cu was higher than 10at.% but lower than 14at.%, two different steps transformations (B2 B19 and B19 B19') occurred; when the content of Cu was 18at.%, only one-step transformation ((B2 B19) occurred. When the annealing temperature rised from 350℃ to 550℃, all of the transformation temperatures (Ms, Mf, As, Af) first ascended and then descended; when the solution temperature rised from 750℃ to 950℃, they descended linearly. The transformation latent heat (△HB2-b19) and the reverse martensitic transformation latent heat (△Hb19-b2) decreased significantly with increasing solution temperatures, and they decreased slightly with increasing annealing temperatures. Research of other alloys showed that heat process had different effect law. The transformation hysteresis and reverse martensitic transformation temperatures decreased abruptly during the initial thermal cycling process and then remained constant with further thermal cycling times (n<4) . The reverse transformation latent heats (△HB19-B2 and △H19-B19) increased with increasing thermal cycling times (n<4), especially △Hb19-b19 increased about by 58%, while the martensitic transformation temperatures and martensitic transformation latent heat ( △HB2-b19) remains almost constant whatever the thermal cycling times. And result of TEM showed that microstructure of TiNi(1-X)Cux at the same time, microstructure of TiNi(1-x)Cux alloy was twin.At the same time, pilot study of Ti50Ni40Cu10(at.%) shape memory alloy thin film was carried out. The thin film was prepared using Pulse Laser Deposition (PLD). Theresearch result showed there were droplets on the surface of the films. And the size and distribution of the droplets were dependent on the deposition conditions. Research of micro-area composition showed that the film was not homogeneous and analysis of composition showed it was slightly different from the target, but comparing with the film prepared by magnetron deposition, the variation rate is very low. It is benefit to the use of such a material whose transformation temperature is sensitive to it's composition.