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Chemical and topological disorderings in the NiTi intermetallic compound during electron irradiation were studied using a combination of in situ irradiation inside a high-resolution high-voltage electron microscope and image analyses of molecular-dynamics-simulated atom configurations. It was found that metastable defect clusters formed during the chemical-disordering phase prior to topological disordering leading to amorphization. These planar defect clusters contributed to the characteristic diffuse scattering were also observed in selected-area diffraction patterns.

In the Mo–Si system, there are three typical intermetallic compounds. In order to get insight into the phase stability under irradiation, interface structure and non-equilibrium phase formation in multilayer materials with several nanometers scale were investigated by means of high-voltage electron microscope. The initial structure was composed of crystalline Mo and amorphous Si layers, and transition layer existed at the interfaces. The thickness of transition layers is thicker at the Mo-on-Si than at the Si-on-Mo interface. While those structures were basically stable after thermal annealing up to 773 K, two types of amorphous layers developed during electron irradiation at room temperature: one is an amorphous-Si layer and the other is a Mo–Si mixing layer. And the radiation-induced amorphization was accompanied by anomalous shrinkage in the thickness of layers. It is suggested that those phenomena are related to non-equilibrium phase formation and biased diffusion process during irradiation.

In order to form the silicide at relatively low temperature, ion-beam-mixing was applied to Mo/Si and Ti/Si systems in a temperature range from room temperature to 473 K. After the irradiation of 1 MeV Si + , the cross-sectional specimens were examined by transmission electron microscopy and X-ray microanalysis. Crystalline silicide formation was achieved only in Mo/Si system irradiated to high dose at each temperature. The evaluation of interdiffusion coefficient indicated that the diffusion is predominant in the ion-beam-mixing process. The nucleation process of silicide and the phase stability are discussed.

In order to improve initial activation properties of TiFe alloy, simple ion implantation and ion mixing with the deposition of LaNi 5 were carried out at room temperature. The results show that argon-ion mixing caused extensive improvement of initial activation, wherein hydrogenation was easily effected at 373 K and 1 MPa. Those results are related to several irradiation effects; the re-crystallization of amorphous film of LaNi 5 and the local segregation of composed elements. Both of these irradiation effects greatly improve the initial hydrogenation process of TiFe alloy.

We have studied nanostructural fluctuations during electron irradiation in the ordered intermetallic compound NiTi by performing irradiation experiments with a high-resolution high-voltage electron microscope (HVEM) and molecular dynamics (MD) simulations. It was observed that atom clusters formed and disappeared repeatedly during irradiation, which results in the structural fluctuation. Comparing the experimental results with the MD simulations, we conclude that such spatio-temporal structural fluctuations under irradiation can be accounted for the evolution of metastable nanoclusters. The present study demonstrates the usefulness of high-resolution HVEM for in situ studies of dynamic, nanoscale fluctuation phenomena.

High-energy ion-beam mixing technique was applied for the surface modification of austenitic stainless steel, followed by electrochemical characterization and microstructural observation. The co-mixing of silicon and chromium resisted the passivation current to 1/1000 relative to the un-modified condition. The corrosion resistance improved remarkably. Microstructural observation revealed that the enhanced diffusion and induced amorphous structure introduced by the co-mixing of silicon and chromium, which played a very important role in the improvement of electrochemical behavior at surface.