CHANGES IN STRUCTURAL-PHASE STATE OF ALUMINUM AL-LOY 7075 AFTER LOW-TEMPERATURE NITRIDING
YTOCPS
DOI:
https://doi.org/10.25712/ASTU.2072-8921.2025.03.041Abstract
The change in the microstructure and phase state of aluminum alloy grade 7075 before and after nitriding was studied. The alloy was produced by the wire-arc additive method, in the substrate area of which columnar grains prevailed, in the central part there were columnar and dendritic structures, the peripheral zone of the manufactured ingot demonstrated equiaxed structures with a grain size of up to 50 μm. The considered structural heterogeneity is caused by the cooling rate of the workpiece, the thermal gradient in the process of layer-by-layer production of the material. Based on the micro-X-ray spectral analysis, the η-phase (MgZn₂) and S-phase (Al₂CuMg) concentrated at the grain boundaries were detected. The alloy is represented by isolated metallic inclusions of Al₂Cu (θ-phase), formed due to slow cooling or overheating of the metal. After nitriding in an arc discharge using a plasma source (hot cathode), the formation of a polycrystalline structure characterized by cell sizes in the range of 60-200 μm was observed in the studied alloy. Single intermetallic compounds MgZn₂ (η) and Al₂Cu (θ) were present in the alloy after low-temperature nitriding. A slight change in the elemental composition of the sample was detected, caused by the plasma nitriding process, which promotes the redistribution of alloying elements with the subsequent formation of a hardened surface layer. The obtained results emphasize the influence of process parameters on the change in the microstructure and phase composition of additively manufactured aluminum alloys after nitriding.
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Copyright (c) 2025 Irina A. Panchenko, Vladislav K. Drobyshev, Sergei V. Konovalov, Dmitry N. Labunsky, Almaz Yu. Nazarov
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