Effect of low-energy proton on the microstructure, martensitic transformation and mechanical properties of irradiated Ni-rich TiNi alloy thin films

Ni–48.5at%Ti thin films were irradiated in the austenite phase by different energy-level protons at a dose rate of 1.85×1012 p/(cm2·s),and the total dose was 2.0×1016 p/cm2.The microstructures of the thin films before and after irradiation were evaluated by transmission electron microscopy(TEM)and grazing-incidence X-ray diffraction(GIXRD),which showed that the volume fraction of Ti3Ni4 phase elevated with proton energy level.The influence of proton irradiation on the transformation behavior of the TiNi thin films was investigated by differential scanning calorimetry(DSC).Compared with the unirradiation film,the reverse transformation start temperatures(As)decreased by about 3°C after 120 keV proton-irradiation.The proton irradiation also had a significant effect on the mechanical properties of the TiNi thin films.After 120 keV energy proton-irradiation,the fracture strength increased by 8.44%,and the critical stress increased by 21.1%.In addition,the nanoindenter measurement image showed that the hardness of the thin films increased with the increase of proton-irradiation energy.This may be due to the defects caused by irradiation,which strengthen the matrix.

Martensitic transformation,shape memory effect and superelasticity of Ti-xZr-(30-x)Nb-4Ta alloys

Martensitic transformations,mechanical properties,shape memory effect and superelasticity of Ti-xZr-(30-x)Nb-4Ta(x=15,16,17 and 18;at%) alloys were investigated.X-ray diffraction(XRD),optical microscopy(OM) and transmission electron microscopy(TEM) results indicated that the Ti-16Zr-14Nb-4Ta,Ti-17Zr-13Nb-4Ta and Ti-18Zr-12Nb4Ta alloys were mainly composed of α″-martensite,while the Ti-15Zr-15Nb-4Ta alloy was characterized by predominant p phase.The reverse martensitic transformation temperatures increased when Nb was replaced by Zr,indicating stronger p-stabilizing effect for the former.The Ti-15Zr-15Nb-4Ta alloy displayed superelasticity during tensile deformation with a recovery strain of 3.51%.For the other three alloys with higher Zr content,the martensitic reorientation occurred during tensile deformation,resulting in shape memory recovery upon subsequent heating.The maximum shape memory effect was 3.46% in the Ti-18Zr-12Nb-4Ta alloy.

Deposition and characterization for high-quality Ti-Ni-Cu thin films with higher Cu content

In order to attain high-quality Ti-Ni-Cu film,the surface morphologies,chemical compositions and mechanical properties of Ti-Ni-Cu thin films prepared by direct current(DC)magnetron sputtering at various processes were characterized by scanning electron microscopy(SEM),X-ray diffractometer(XRD)and tensile tests.The type of substrates,Ar pressure and sputtering power had significant effects on the quality and chemical composition of Ti-Ni-Cu thin film.Compared with Si and SiO_(2) slides,it was easier to obtain freestanding films by adopting glass or piezoid slide as substrates.The Ti-Ni-Cu thin film deposited at lower pressure(0.10 Pa)had a better density.The surface was featured with porous structure in the Ti-Ni-Cu thin film prepared by higher Ar pressure of 0.36 Pa.In addition,both the tensile strength and strain of annealed Ti-Ni-Cu thin film continuously increased with Ar pressure decreasing.Higher density contributed to the superior mechanical properties.The deposition rate firstly increased and then decreased with Ar pressure and sputtering power increasing.The composition of deposited Ti-Ni-Cu film can be tailored by changing sputter power.The deposited Ti-Ni-Cu thin films at different processing parameters were in amorphous state.In short,the present study offered the important theoretical basis for the preparation of Ti-Ni-Cu thin film with higher quality and performance.