Microstructure of Nitrided AA5052 Aluminum Alloy Formed by Electron Beam Excited Plasma Technique

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: cryslallographic structure (X-raypowder 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 μm. In the AlN layer, pillar-shaped 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 .