64keV Ni ion implantation was performed at room temperature up to a dose of 131017 cm22 in a-Al2O3 single crystals. The charge states, structure, and optical properties of metallic embedded Ni nanoparticles were studied by using x-ray photoelectron spectroscopy (XPS), transmission electron microscopy, and optical spectroscopy, respectively. XPS analysis showed that implanted Ni ions are mainly in charge state of metallic Ni0. Nanoparticles distributed from the surface to 30 nm below the surface were observed in a high-angle annular dark-field image. The size of nanoparticles ranges from 1 to 5nm in diameter. A high-resolution electron microscopy image indicated the Ni-implanted area had been entirely amorphized. A new broad absorption band centered at 400nm appeared in the optical absorption spectrum of the as-implanted crystal, due to surface plasma resonance of Ni nanoparticles. We did not find any emission band in the as-implanted sample under a Xe lamp excitation wavelength of 250-430nm in a spectrophotometer.

A model is proposed for the calculation of the irradiation induced changes of the martensitic transformation temperatures of shape memory alloys. It considers the transition temperatures being determined by a chemical and a non-chemical term in the Gibbs free energy that can be affected by the irradiation induced changes of the vacancy density and the chemical ordering of the crystal structures. Numerical simulations for TiNi SMAs have shown that upon irradiation the austenite finish temperature Af can be raised slightly at the beginning stage. After that, both Af and the martensite start temperature Ms will decrease strongly and reach some stable values after extensive irradiations. Both the dose rate and the temperature of irradiations will affect the changes of Ms and Af. According to the simulation, the increase of Af at the beginning of irradiations is resulted from the irradiation induced point defect production that increases mainly the non-chemical term in the Gibbs free energy change of the martensitic transformation. The irradiation induced chemical disordering reduces both the chemical and non-chemical terms in the Gibbs free energy change and leads to the strong decreases of Ms and Af.

TiNiCu shape memory alloy samples were irradiated by 1.7MeV electrons below the martensite finish temperature Mf. The transformation temperatures and the latent heat of phase transformation were measured by differential scanning calorimeter. The damage accumulation was determined by positron annihilation technology. The results indicated that the austenite transformation temperatures were raised, and the hysteresis was increased by the irradiation. The electron irradiation had a slight effect on Mf, and no detectable effect on the martensitic transformation start temperature Ms. The second lifetime of positrons were increased by the electron irradiation indicating the increase in the size and amount of vacancy clusters, which contributed to the observed change of the transformation characteristics.

The structural mechanisms of the hardening of a Ti-2Al-2.5Zr alloy by 75 keV nitrogen ion implantation with doses of 3310 and 17 2 8310 N/cm is investigated. The surface characterization of samples was studied by XPS, XRD and Vickers hardness tests. The results of XPS and XRD analysis show that TiN is formed in the surface region. Nitrogen implantation increases the surface hardness up to 340 17 17 2 and 260% for doses of 8310 and 3310N/cm, respectively, due to formation of TiN and irradiation-enhanced hardening.

The incomplete transformations of near equiatomic TiNi shape memory alloys were investigated by differential scanning calorimeter (DSC). The results showed that the incomplete transformation can induce multistage phase transformation in a sample showing R-phase transformation, when the turn back temperature located in a value between Rf and Ms, the heat flow detected upon following heating only shows one endothermic peak. With decreasing the turn back temperature to a temperature between Ms and Mf, two endothermic peaks (multistage phase transformation) can be observed upon the following heating. There were no incomplete transformation induced multistage phase transformations in a sample without R-phase transformation.