Aluminum, Nitrogen Ion Implantation Study

After nitrogen implantation into aluminium, a portion of nitrogen created metallic compound hexagonal AIN (rather than cubic AIN) in combination with aluminium matrix, the rest distributed in aluminium in the form of interstitial atoms. The aluminium surface implanted with nitrogen was completely covered with spherical spheroidal and rod-like nodules, the size and denseness of which varied with sputter time increasing. The recrystallization of surface layer of Al matrix occurred after N-implantation, which tended to strengthen the preferred orientation of Al (200) plane.The AIN particles formed on the surface of aluminium subjected to 7 × 10¹⁷ N⁺/cm² dose implantation at 60 keV were about 28nm which were very fine. The diffraction peaks of AIN got diffused and broad due to the fine AIN grains and the orientation relationship between f.c.c aluminium and the initiated AIN (i.e.{111}_A1 {0001}_A1N <110>_A1 <11 20>). After N-implantation, the near surface microstructure consisted of three regions, the outermost one being AL₂O₃ and the intermediate AIN and the innermost Al matrix.The nitrogen dose exerted a great influence on the structures and wear properties of the aluminium implanted with nitrogen. When the dose was low, the supersaturated solid solution of nitrogen formed due to nitrogen occupation of tetrahedral interstices of the parent f.c.c aluminium. Nitrogen created metallic compound AIN in combination with aluminium matrix and the amount of AIN increased with the nitrogen dose increasing. The amount of AIN reached the peak value in the dose of 7 × 10¹⁷N⁺/cm². After that. AIN itself was solid-solution-strengthened when the dose was further increased; As a result, the wear performance of the aluminium implanted with nitrogen improved gradually with the increasing nitrogen dose; The dominant wear mechanism for the unimplanted sample was adhesive wear, but with the nitrogen dose increasing it changed from adhesive wear to abrasive one gradually.The nitrogen dose also exerted a great influence on the nanohardness of the aluminium implanted with nitrogen. The nanohardness increased with the nitrogen dose increasing but decreased when the penetrating depth increased, which justified the relationship between the friction coefficients of the aluminium implanted with nitrogen and wear cycles under weak contact condition. The elastic modulus of the aluminium implanted with nitrogen whose dose was not more than 5×10¹⁷N⁺/cm² changed little compared with unimplanted aluminium; when the nitrogen dose was more than 7×10¹⁷N⁺/cm², its elastic modulus increaseddramatically in relation to unimplanted aluminium but decreased with the increasing penetrating depth.Nitrogen implantation also impacted corrosion-resistance very much. When the dose was low, the corrosion-resistance improved with the increasing nitrogen dose but it didn't improved monotonically when the dose increased gradually. When the dose was in the range of middle value (about(3 5)× 10¹⁷N⁺/cm²), the corrosion-resistance deteriorated with the rising dose. Implanted with much more nitrogen, the corrosion-resistance of aluminium improved once again.The nitrogen distribution in Al after nitrogen implantation was simulated utilizing TRIM'98 code. The results showed that the content of nitrogen in Al matrix presented gaussian-like distribution, in good agreement with AES depth profile. The radiation damage was also calculated employing the Kinchin-Pease displacement model, which demonstrated that the radiation damage distribution was a far cry from the gaussian-like one and closer to the sample surface compared with projected range distribution. And nitrogen implantation into aluminium provided the energy required for dislocation generation.