a b s t r a c tSelf-propagating high-temperature synthesis (SHS) was previously proposed as alternative preparation route for FeeAl intermetallics. However, this process was not optimized and the mechanism and kinetics of the phases' formation was not fully clarified up to current days. In this work, in situ high energy X-ray diffraction analysis was carried out during the SHS process and the mechanism of the intermetallic' formation in FeAl25 powder mixture was described during rapid heating and isothermal annealing at 800 C as well as during a slower continuous heating to 900 C. During slower heating, the formation of Fe 2 Al 5 and FeAl 2 intermetallics starts below the melting point of aluminium. When the heating rate is high, intermetallics are created after melting of aluminium. During long-term annealing, all of the phases can be transformed to FeAl phase when fine powders were applied. Detailed mechanism is proposed in this paper and kinetics of the intermetallics' formation is described.

Rapidly solidified alloys, based on an aluminium-transition metal (TM) system, are promising structural materials. They show good mechanical properties and excellent thermal stability, which is caused by the very fine nanostructure of these materials and by the presence of nonequilibrium intermetallic phases. Influence of the cooling rate and Ce addition on properties of Al-5.5Ce-3Fe-1.5Ti alloy that was prepared by the melt spinning method was studied in this work. It was shown that formation of the quasicrystalline phase depends on the cooling rate during melt spinning. The addition of a few weight percents of Ce modifies phase composition of the alloy and stabilizes quasicrystals at elevated temperatures. However, the influence of Ce addition on hardness was not observed.

No abstract

No abstract

The presented article deals with the assessment of titanium dioxide nanotube microscopic images by means of imageprocessing methods. Inner diameter, wall thickness, and fraction of intertubular space are among the basic parameters characterizing the quality of nanostructured material. These parameters are especially important during the process of nanomaterial development. Nanostructures were prepared by electrochemical oxidation on the surface of Ti-6Al-4V alloy. Results of this process are greatly influenced by the chosen experimental conditions, so objective evaluation of experimental results is very important for the optimal setting of experimental parameters. Image-processing methods could be successfully applied to microscopic images to obtain the aforementioned objective characterization criteria. Various methods, such as object classification, image filtering, and mathematical morphology, could be taken into consideration with respect to a specific type of image data. In addition, the algorithm proposed uses the advantages of adaptive thresholding, watershed transform, low-pass filtering, mathematical morphology and cluster analysis. The nanotube wall thickness evaluation is suggested by two different approaches for the characterization of variable quality of the images processed.