Papers by Author: Anna Góral

Abstract: Our interests are focused on the Ni/Al₂O₃ nanocomposite coatings electrochemically deposited in modified Watt’s-type baths into which α-Al₂O₃ nanopowder is added on steel substrates. The effect of different amounts of α-Al₂O₃ phase in the electrolyte baths on microstructure of electrodeposited Ni/Al₂O₃ coatings is investigated. In order to study the coatings the non-destructive X-ray diffraction techniques are applied. As indirect techniques, they are supported by imaging methods, especially scanning electron microscopy.

Abstract: In the present study, the electrodeposition of composites consisted of metal matrix (nickel) and inert particles (hard nano-sized Al2O3 oxide) has been carried out in a Watt’s type bath of pH 4, at room temperature in a system with the steel rotating disk electrode. The influence of dispersed Al2O3 powder on structure characteristics (morphology, phase composition, texture, residual stresses) of Ni/Al2O3 coatings has been investigated. The crystallographic texture of Ni and Ni/Al2O3 coatings deposited on the steel substrates was analyzed by XRD technique based on the back-reflection pole figures. The “sin2ψ” X-ray diffraction method was used to determine the residual stress as a function of X-ray penetration depth. The influence of Al2O3 particles on the value of the Ni coating microhardness was also analyzed.

Abstract: The effect of rapid solidification on the microstructure of Al-Zn-Mg-Cu alloys with 8 wt.% Zn-2 wt.% Mg-2.3 wt.% Cu and 0.2 or 0.5 wt.% of Zr additions were investigated using X-ray diffraction measurements (XRD), scanning (SEM) and transmission electron microscopy (TEM) combined with energy dispersive X-ray (EDX) microanalysis. Rapidly solidified ribbons with thickness of 70-100 m were performed by melt spinning technique. The mould cast alloys as well as the melt spun ribbons revealed dendritic microstructure of (Al) solid solution and η Mg(Zn,Cu)2 phase in interdendritic areas. The refinement of the microstructure and reduction of the volume fraction of the η phase up to 1.7%, as compared to 4% in the mould cast alloys was observed in the ribbons. Copper dissolution up to about 20 wt % in the η phase causes a decrease of the lattice parameters. The Al3Zr primary precipitates were observed in the mould cast alloy containing 0.5 wt % of Zr while in the ribbons all zirconium dissolved in the aluminium solid solution.