Effect of Nitriding on the Microstructure and Mechanical Properties of AA7075 Alloy

Abstract

In this paper, we investigated the 7075 aluminum alloy obtained by casting in the as-delivered condition and after nitriding the alloy in an arc discharge using a plasma source with a hot cathode at a temperature of 350°C for 2 h in a gas mixture of 50% argon and 50% nitrogen, 0.5 Pa, 500 V. The surface of the sample after nitriding was represented by a grain structure with a nonuniform distribution of manganese, iron, and oxygen atoms. Nitriding contributed to an increase in the nanohardness of the material to 1.4 GPa and the Young’s modulus to 132 GPa, owing to the formation of a modified layer after nitriding the alloy surface. The depth of the nitrided layer of the studied aluminum samples was nonuniform and varied from 5 to 10 µm; in the cross section of the studied layer, areas with increased oxygen and manganese content were detected using the elemental mapping method. The average value of the crystal lattice parameter after nitriding of the material changed from 4.035 to 4.047 Å. This increase in the crystal lattice parameter may be associated with the formation of tensile macrostresses, which affect the mechanical properties of the material.