The nitriding of the AA5052 aluminum alloy was carried out using an electron beam excited plasma (EBEP) technique. The specimen was characterized with respect to the following properties: crystallographic structure (X-ray powder diffraction) and the surface and cross sectional microstructures of the nitrided layer (AlN layer) observed by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The AlN layer was uniformly formed on the AA5052 alloy with the thickness of around 4-5 mm. In the AlN layer, pillarshaped grains were formed perpendicular to the surface with different orientations. The average grain size near the interface between the substrate and the AlN layer was smaller than that near the surface of the AlN layer. On the surface of the AlN layer, the nitrogen concentration was high, and in the middle of the AlN layer, it had a constant concentration like aluminum, and the concentration decreased as it approached the interface. The magnesium concentrates at the interface due to the formation of MgAl 2 O 4 .

Microstructure and property modifications of an AISI H13 (4Cr5MoSiV) steel induced by pulsed electron beam treatment J.Nitriding of a tool steel was carried out with an electron-beam-excited plasma ͑EBEP͒. EBEP is sustained with energetic electron beams over the pressure range of 10 −3 -10 1 Pa by electron-impact ionization. Samples whose temperatures were controlled by electric radiant heater were exposed to EBEP. A nitrided layer of 100 m and a surface hardness of 1000 HV͑0.1͒ were achieved for tool steel SKD61 ͑JIS͒ at 800 K and a treatment time of 3 h. In order to measure the density of nitrogen atoms in EBEP, a vacuum ultraviolet absorption spectroscopy system was used. It was found that the density of nitrogen atoms increased from 10 11 to 10 12 cm −3 linearly with an increase of electron beam current from 2 to 20 A.

A Zn atom is employed as the light source for optical resonance pumping to a high lying energy level of the Cu atom, thereby depopulating both the Cu lower laser level and enhancing the upper laser level via cascading decays that is carried out simultaneously. The width of the lasing pulse broadened by 220% and the peak value increased by 180%. The cascading decay route was clarified by observing the fluorescence lines, λ=675.1, 793.5, and 809.0 nm, thereby specifying five levels of excitation loop.

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