| Popis: |
One of the non-linear long-range effects of the interaction of intense-pulsed-ion beams (IPIB) with metals is their anomalous hardening in non-radiated regions. In experiments reported here, the IPIB parameters were: ion energy (70% C + , 30% H + ) E =0.2 to 0.6 MeV; current density j =20 to 250 A cm −2 ; pulse duration 60 to 100 ns; and fluence 1 to 6 J cm −2 pulse −1 . For j >90 A cm −2 , together with the known increase in microhardness ( H 0 ) observed in the irradiated region, a second peak at H z =(0.6 to 0.8) H 0 was found at the depth x = z =(40 to 100) R 0 , where R 0 is the ion-beam range (∼1 μm). H z and z values depend on the type of metal and irradiation regime. This anomalous hardening induces different local deformation states, which are the result of the generation and interaction of point (interstitials, vacancies) and linear (e.g., dislocations) defects in the shock-wave field. We used the recoil nucleus method for analysis of the deformation states after irradiation. Non-radiated and irradiated lead samples were saturated by hydrogen gas. Lead was selected because it should not react with hydrogen. The magnitude of hydrogen saturation, n h , is low in regions of compressive stress (because of the high concentration of interstitials) and high in tensile stress regions (because of the high concentration of vacancies). A primary 4 He 2+ -ion beam with an energy of 3.0 MeV was scanned on the transverse cross-section of the lead samples. The excited hydrogen recoil nucleus was knocked forward and registered by the detector. The hydrogen concentration n h ( x ) was uniform for non-irradiated samples, but had maxima and mimima for irradiated ones. In addition, the f -parameter distribution (obtained from annihilation photon angular distribution curves) with depth has been studied. A correlation is observed for all three kinds of H ( x ), n h ( x ) and f -parameter distribution that proves the proposed mechanism of hardening. |
Full Text from ScienceDirect