Application of the stereomicrophotogrammetric method for the complex study of the Al-Cu-Mg alloys system

Abstract

Purpose. To combine the stereophotogrammetric method for processing fracture surface images at the micro level with the results of a series of mechanical and metal fractographic studies with precision methods for scanning electron microscopy (SEM) and energy dispersive analysis (EDX) in order to determine the peculiarities and general laws of the fracture process of Al-Cu-Mg test samples. Methodology. In this work, the mechanical properties of Al-Cu-Mg samples after mild (recrystallization) annealing and subsequent natural aging and a sample without heat treatment were experimentally determined. At the next stage, SEM-stereomicrofractographic research on fractures and their three-dimensional reconstruction from the obtained stereo images were performed. EDX studies have been performed on various parts of the samples to determine the distribution of mass percentages of elements in the study areas. A comprehensive methodology for experimental studies of Al-Cu-Mg alloys was used in this work to obtain qualitative and quantitative information on the microstructure of fractures, which consisted of the following steps: determination of the mechanical properties of samples by traditional methods of macro- and microanalysis; study on stereopairs of the microstructure of fractures by the stereophotogrammetric method; identification of the chemical composition and structure of matrix precipitation particles by energy dispersive X-ray spectroscopy (EDX analysis). Findings. Our experiments have shown that with an increase in the time of natural aging, the hardness increases slowly and reaches a maximum hardness of 127 Hv30 after 97 hours, which does not decrease subsequently. After natural hardening, the average fracture strength increases to Rm 440.3 with a relative elongation of 21.8 %. Mechanical tests have shown that the tensile strength increases with the hardness value and, in contrast, the toughness decreases. The energy required to fracture the sample is 16 J, followed by transcrystalline cellular fracture. The precipitates have a diameter of approximately 2.5–3 microns. Originality. Comparing the results of mechanical and metallographic studies, it can be argued that the desired properties of Al-Cu-Mg samples appear after dispersion hardening, which confirms the optimal hardening conditions. The results of the photogrammetric evaluation of samples in the micro range demonstrate the flexibility and accuracy potential of photogrammetric measurement methods and their subsequent processing, interpretation, and integration with EDX analysis to select optimal study sites. Practical value. An integrated approach to the analysis of materials using the SEM stereomicrophotogrammetric method, mechanical and metallographic studies, and EDX analysis was tested in this work.