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Abstract: The dry sliding tribological behavior of AZ31 magnesium alloy irradiated by high-intensity pulsed ion beam (HIPIB) at energy density of 3.4J/cm2 with 10 shots is investigated by dry sliding wear tests in order to explore the effect of HIPIB irradiation on tribological property of magnesium alloy. Surface morphologies, composition and structure of the irradiated AZ31 magnesium alloys are examined by electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results indicated that HIPIB irradiation led to the increase in surface microhardness and the reduction in friction coefficient and wear rate. Wear rate for both the original and the irradiated samples increased with increasing sliding load from 0.1 to 0.5N. The transition from severe metallic wear to mild oxidative wear induced by HIPIB irradiation was observed by a combined analysis in surface morphology and chemical composition of wear tracks, mechanically mixed materials and wear debris, which is mainly attributed to the significant increase in microhardness resulting from grain refinement on the irradiated surface. In addition, defects induced by HIPIB irradiation promoted the diffusion of oxygen during sliding wear and therefore led to the formation of compact mixed materials and protective films on the wear tracks surface, which also contributes to the transition in wear mechanism of AZ31 magnesium alloy induced by HIPIB irradiation. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure and morphology of graphite irradiated by high-intensity pulsed ion beams (HIPIB) has been studied by varying the ion current density as 200, 350 and 1500A/cm2 with one to five shots. Phase transformation from graphite to diamond-like carbon (DLC) on the HIPIB-irradiated graphite was confirmed by Raman spectroscopy where a typical broadened asymmetric peak appeared in the wavenumber range of 1100–1700cm−1. Formation of DLC on the irradiated graphite strongly depended on the HIPIB parameters and preferably took place at the medium ion current density of 350A/cm2 up to five shots. Numerical simulation of ablation process was performed to explore the transformation mechanism of DLC from graphite irradiated by HIPIB. The calculation showed that the temperature profile in irradiated graphite at 350A/cm2 is almost identical to that at 200A/cm2, showing a deeper heat-affected zone in comparison with that of 1500A/cm2. Moreover, the ablation depth per shot is around 0.8μm at 350A/cm2, higher than that of 0.4μm at 200A/cm2 and much lower than that of 8.4μm at 1500A/cm2, respectively. The experimental and numerical results indicate that a proper temperature and pressure repetitively created in the top layer of ablated graphite during HIPIB irradiation facilitates the phase transformation. [Copyright &y& Elsevier]

Abstract: Droplet behavior from the surfaces of pure metals Ti and Al ablated by high-intensity pulsed ion beam (HIPIB) with an ion current density from 30 to 200A/cm2 has been investigated to explore the mechanism of mass transfer on HIPIB-irradiated materials. Droplet ejection on the ablated metal surface is studied by scanning electron microscope observation, energy dispersive X-ray spectroscopy analysis and profilometer measurement. The presence of ejected droplets from the irradiated surfaces is detected on both the surfaces of irradiated metals and substrates locating adjacent to the ablated surfaces. Moreover, the number density of droplets observed on both the surfaces tends to increase with increasing the ion current density. This phenomenon correlates to the fact that higher ion-beam intensity led to a more intense ablation, i.e. a severer droplet ejection. In addition, surface roughness (R a) for the respective metals is continuously increased with increasing the ion current density, indicating a more significant disturbance on the melted surfaces caused by the correspondingly severer droplet ejection. Combined with the previous finding of selective ablation on titanium, it is concluded that the droplet ejection is the efficient cause of cratering and disturbance on HIPIB-ablated surfaces. [Copyright &y& Elsevier]