Study On Preparation And Characterization Of Chilling Ti-Ni Alloy Ribbons

In order to develop the micro-actuator materials with fast response using in micro-electro-mechanical systems(MEMS),the chilled Ti-x Ni(x=45 ~ 49.8 at.%)shape memory alloy ribbons were fabricated by melt-spinning in this research.The effects of Ni content,copper roller speed and the annealing processes on microstructure,phase composition,phase transformation behaviors and shape memory effect of alloy ribbons were investigated by X-ray diffraction(XRD),confocal laser scanning microscope(CLSM),differential scanning calorimetry(DSC)and bending test.The results are as follows.The composition phases are martensite(M)(B19ˊ phase,monoclinic structure)and parent phase(A)(B2 phase,Cs Cl-type structure),the microstructure morphology is vertically and horizontally arrayed columnar,and are all of excellent shape memory effect in as-cast and annealed chilling Ti-x Ni(x=45 ~ 49.8 at.%)alloy ribbons.In the range of Ni content of 45~48 at.%,the A→M/M→A type reversible martensitic transformation occurs upon cooling and heating.When Ni content is 49 at.% and 49.8 at.%,the A→R→M two-stage martensitic transformation occurs upon cooling,the M→A one-stage martensitic transformation occurred upon heating.With the increase of Ni content,the martensitic transformation temperature(TM),the martensitic reverse transformation temperature(TA)and the temperature hysteresis(ΔTM)are increase.The shape memory effect is optimal when Ni content is 47 at.%.When the alloy ribbons are prepared,with increasing the roller speed,the grain size is small,the phase transformation types do not change,the TM temperature decrease,and the recovery rate of shape memory increases in Ti-47 Ni,Ti-48 Ni and Ti-49 Ni alloy ribbons.With the increase of copper roll speed,the temperature hysteresis decreases in Ti-49 Ni alloy ribbon,the temperature hysteresis increases and then decreases in Ti-47 Ni and Ti-48 Ni alloy ribbons,and the maximum temperature hysteresis is obtained when the roll speed is 1000 r/min.The annealing temperatures do hardly affect the composition phases and microstructure morphology of Ti-Ni shape memory alloy ribbon,while affect the transformation behaviors and shape memory effect of alloy ribbons.A→M/M→A type martensitic reversible transformation occurs in annealed Ti-45 Ni and Ti-47 Ni alloy ribbons upon cooling and heating.With the increase of the annealing temperatures,the transformation temperature,the temperature hysteresis and the recovery rate of shape memory of alloy ribbons fluctuate in a small area.A→M/M→A type martensitic reversible transformation occurs in annealed Ti-49 Ni alloy ribbon upon cooling and heating.The phase transition temperature of the alloy ribbon increases with the increase of the annealing temperature.The TM temperature increase from 38.92 ℃ to 61.19 ℃ when the annealing temperature increase from 600 ℃ to 900 ℃.The shape memory effect of annealed Ti-47 Ni alloy ribbon is best.