The chemical composition, structure, and physical properties of aluminum nitride (AlN) films obtained using pulsed DC reactive magnetron sputtering in asymmetric bipolar mode have been studied. X-ray diffraction and electron diffraction confirmed the composition of c–axis textured hexagonal AlN films required for piezoelectric applications. The surface of the films obtained is quite smooth; the arithmetic average roughness does not exceed 2 nm. Transmission electron microscopy has shown the presence of a transition layer at the film–substrate interface. Transmission electron microscopy and X-ray photoelectron spectroscopy depth profile analysis have shown that the films have an oxidized surface layer which has an influence on the optical model of the films derived from ellipsometric data. However, it does not significantly influence the films’ piezoresponse. Piezoelectric force microscopy indicated a piezoelectric effect in the films that is uniform over their surface.

Composite thin films of the AlN–Al–V type, grown by magnetron sputtering, were analyzed by several complementary diagnostic methods. The power of the magnetron was used as a variable parameter, while gas flows, chamber pressure, and substrate temperature remained unchanged during the film fabrication. According to grazing incidence X-ray diffraction (GIXRD) results, in most cases, it was possible to obtain an (002)-oriented aluminum nitride (AlN) layer in the films, although, with an increase in the magnetron power to 800 W, the formation of X-ray amorphous AlN was observed. Similarly, according to the Raman results, the width of the peak of the vibrational mode E1, which characterizes the correlation length of optical phonons, also significantly increased in the case of the sample obtained at 800 W, which may indicate a deterioration in the crystallinity of the film. A study of the surface morphology by atomic force microscopy (AFM) and scanning electron microscopy (SEM) showed that the AlN film grows in the form of vertically oriented hexagons, and crystallites emerge on the surface in the form of dendritic structures. During the analysis of the AFM roughness power spectral density (PSD-x) functions, it was found that the type of substrate material does not significantly affect the surface roughness of the AlN films. According to the energy–dispersive X-ray spectroscopy (SEM-EDS) elemental analysis, an excess of aluminum was observed in all fabricated samples. The study of the current-voltage characteristics of the films showed that the resistance of aluminum nitride layers in such composites correlates with both the aluminum content and the structural imperfection of crystallites.

The work represents the results of mechanical tests and structuralphase analysis of the 1441 (AlCuMgLi) alloy laser weld joints. Synchrotron X-ray diffraction showed that laser welding causes the formation of T3 and T2 phases instead of strengthening δ' phase in weld material. Applied post-weld heat treatment (PWHT) restored the original phase composition but led to ~5 times growth of the δ' phase precipitates. As a result, weld joints returned and even exceeded the ultimate yield tensile strength of the base alloy but their tensile strain was notably lower. Fatigue tests demonstrated that the obtained weld joints had high fatigue resistance significantly exceeding riveted joints even before PWHT. Heat treatment increased fatigue resistance at high loads but reduced this property at low load.