Composite wires obtained from aluminium shell, micron sized aluminium powder and nano - sized TiN, SiC and Al2O3 powders were fabricated by a two stage process. The stages included ultrasonic treatment and hot extrusion. TEM and SEM observations were performed to investigate the wires’ microstructure. Individual nano powder particles as well as particle agglomerations were observed by two microscopic methods, as well as nanoparticles distribution and localization in the matrix. It was found that the observed nanoparticles and clusters were in the volume of micron-sized Al particles and along the grain boundaries of the matrix. The provided EDX analysis confirms the presence of nanoparticles in the aluminium matrix. From the obtained results, it can be concluded that the two stage fabrication process of nanocomposite wires leads to better wetting of the nano powders from the aluminium melt. Nanocomposites obtained by mixing and extruding TiN, SiC and Al2O3 nano powders and Al micro powders can be used as modifiers of aluminium alloys, as the nanoparticles will contribute to grain refinement and will participate as additional crystallization centers.

Two types of A356 alloy castings in initial and modified with nanoparticles condition produced by gravitational casting were studied. Samples, as-cut from the castings, were subjected to light optical microscopy (LM), thermal analyses, Electron Backscattered Diffraction (EBSD) and Scanning Transmission Electron Microscopy (STEM) analyses. Results, obtained by EBSD, confirmed that there is grain refinement in samples from castings with added nanoparticles compared to the initial ones. STEM analysis shows agglomerates of nanoparticles in examined foils. Nanoparticles’ position in the microstructure confirms the hypothesis that they act as nucleating sites during the alloy solidification, which is the reason for observed fine-grained microstructure.