| High-intensity pulsed ion beam(HIPIB) technique has been progressively developed as a unique approach for surface modification of materials in the recent years. Generation of high-stability HIPIB for practical application necessitates fully understanding the characteristics of the magnetically insulated ion diode(MID). In this work, effect of the lifetime of anode polyethylene sheet on HIPIB generation from the MID with an external-magnetic field has been studied systematically to obtain the optimized ion beam parameters. Based on the achievement of high-stability HIPIB generation, the dynamic behavior of HIPIB-irradiated materials has been subsequently investigated to clarify the mass transfer mechanism on the different ablated surfaces of metallic materials, the formation and propagation of the induced stress wave in the irradiated materials, and the hardening mechanism of the irradiated materials, providing an experimental evidence with a further understanding of exploring the interaction mechanism between HIPIB and materials.Study of lifetime of anode polyethylene in the MIDs with an external-magnetic field operated in unipolar pulse mode has been carried out in parallel on TEMP-6 and ETIGO-2 HIPIB apparatuses. The discharge times of anode polyethylene sheet in the TEMP-6 HIPIB apparatus can reach to 500-700 pulses at a peak diode voltage of 420 kV, where the cathode with improved structure works as a "close" magnetic coil that effectively increases the continuity and uniformity of magnetic field. As for the MID in ETIGO-2 HIPIB apparatus, the distribution of the magnetic field is not so uniform due to the presence of an opening in the cathode, resulting in a much shorter lifetime of anode polyethylene with 2-4 pulses during discharging at a higher peak diode voltage of 1100 kV. The anode plasma is produced during the surface discharging process on polyethylene sheet under the electrical and magnetic fields in MID, i. e. high-voltage surface breakdown. The electron avalanche under the discharging process causes formation of discharge channels on the anode polyethylene surface. The bombardments of energetic electrons and ions lead to the surface roughening of the anode polyethylene, and the polyethylene in the surface layer degrades into low-molecular-weight polymer, resulting in the decrease of ion current density and the poor stability of HIPIB extraction. The stabilized discharge of anode polyethylene can exceed 1000 pulses through changing the anode polymer, and optimizing the structure and impedance of MID.HIPIB irradiation of pure Ti and Al was performed at the ion current density of 30-1500 A/cm2 with 1 shot. Surface roughness (Ra) of the irradiated surfaces increased with increasing the ion current density for both the metals. The values of Ra increased from 0.227μm and 0.185μm for the non-irradiated Ti and Al to 0.639μm and 0.372μm for the irradiated Ti and Al at 200 A/cm2, respectively. The selective ablation originated from surface irregularities with a preferential heating effect was confirmed by the irradiation and deposition experiments where the droplet ejection was detected on the irradiated Ti and Al surfaces. And the droplet ejection caused the disturbance features of crater and waviness on the ablated surface. As increasing the ion current density, droplet ejection became severer on the irradiated surface and resulted in the significantly roughening of the irradiated surface.The stress waves induced in the irradiated materials, i. e. pure Al, Ti, Cu and plasma sprayed ZrO2 thermal barrier coating(TBC) on heat-resistant steel, have been measured in situ by using lead-zirconte-titanate(PZT) piezoelectric sensor with central frequency of 10 MHz during HIPIB irradiation at the ion current density of 30-350 A/cm2 with shot nurnber of 1-10. With increasing the ion current density from 100 to 350 A/cm2, the magnitude of stress wave for pure Al increased from 2 to 80 MPa. At 350 A/cm2, the peak intensity of stress wave was 70-90 MPa and 27-40 MPa for the irradiated Al and Ti with 1-10 shots, respectively. And for TBC, the value decreased to 15-20 MPa. Two mechanisms account for the generation of Stress wave, i. e. thermoelastic and recoil, which resulted in the fomation of thermoelastic stress wave and recoil stress wave, respectivly. The intensity of recoil stress wave increased apparently with the increase of ion current density. Under the same HIPIB irradiation parameters, the intensity of induced stress wave on the materials with low melting temperature was higher than that of the materials with high melting temperature, due to the different melting and evaporation behavior on the irradiated surface. The structue of TBC with microcracks and cavities weakened the induced stress wave and changed the propagation process.Pure Cu was irradiated by HIPIB with the ion current density of 100-350 A/cm2 and shot number of 1-10. The surface roughness of pure Cu firstly decreases and then increases as increasing the ion current density and the shot number. Ra decreased from 0.12μm for the non-irradiated surface to 0.09μm for the irradiated Cu at 100 A/cm2 with 1 shot. The maximum roughness of 0.51μm was found at 350 A/cm2 with 10 shots. The microhardness of the irradiated Cu increased with increasing the ion current density and the shot number, where the value increased nearly 70％at 350 A/cm2 with 10 shots with the respect to the non-irradiated one. The hardened layer of the irradiated Cu at 100 A/cm2 with 10 shots reached to 100μm, and the maximum thickness was 300μm under the irradiation condition of 350 A/cm2 with 10 shots. HIPIB irradiation caused the grain refinement and increased the density of defects in the hardened layer, such as dislocations and twins etc. This shock-hardening effect is attributed to the strengthening resulted from the stress on the irradiated Cu surface and induced recoil stress wave. Based on the ball-on-disk wear tests, the duration of running-in stage depends on the roughness and the hardness of irradiated Cu surface. While the steady-state friction coefficient was mainly influenced by the hardness and the depth of hardened layer. For the irradiated Cu at 350 A/cm2 with 10 shots, the friction coefficient decreased to a value of 0.45 from 0.9 for the non-irradiated Cu. Correspondingly, the depth of worn track significantly decreased from 20μm to 0.8μm.HIPIB irradiation into Al-Cu alloy was performed at the ion current density from 100 to 350 A/cm2 with shot number of 1-10. It was found that the surface roughness increased with increasing the ion current density and the shot number. The maximum Ra of 0.5μm was obtained at 350 A/cm2 with 10 shots. A melted layer of 5-6.5μm thick induced by HIPIB was formed on the Al-Cu alloy, with a straight interface between the melted layer and Al-Cu matrix. The microhardness of remelted layer increased as increasing the ion currednt density, and showed little change with increasing the shot number. The maximum value of microhardness was detected for the irradiated Al-Cu alloy with 350 A/cm2 at 1 shot, with an increase up to 50％as compared to that of the non-irradiated Al-Cu alloy. The depth of hardened layer was about 50μm for the irradiated Al-Cu alloy, at 100 A/cm2 with 10 shots, and increased to 150μm at 350 A/cm2 with 10 shots. HIPIB irradiation resulted in the Cu supersaturated solution in Al lattice and the increase of defects density in the melted layer. This shock-hardening effect of Al-Cu alloy under HIPIB irradiation is attributed to the solution strengthening and the hardening by the induced recoil stress wave. The ball-on-disk wear tests demonstrated that the wear-resistance of irradiated Al-Cu alloy was influenced by the hardness and the depth of hardened layer. At 200 A/cm2 with 10 shots, the depth of worn track on the irradiated Al-Cu alloy decreased to 6μm compared with that of 10μm for the non-irradiated one.
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