Optical Monitoring in Elaboration of Metal Matrix Composites by Direct Metal Deposition

AbstractDevelopment of composites with multi-functional properties is a challenging problem that could be solved by laser cladding. The objective of the present work is to demonstrate the advantages of optical monitoring in optimizing deposition of carbide-reinforced metal matrix composites. Multi-wavelength pyrometer and infrared camera are applied to analyse high temperature heat – and mass transfer in the cladding zone. The influence of laser power, laser cladding speed and powder feeding rate on the brightness temperature are studied. The thermal images of the molten pool obtained by infrared camera for different TiC contents in the powder blend are analysed as well as the beads geometry, microstructure and microhardness

Thermal stability of the cellular structure of an austenitic alloy after selective laser melting

Published ArticleThe thermal stability of the cellular structure of an austenitic Fe–17% Cr–12% Ni–2% Mo–1% Mn–0.7% Si–0.02% C alloy produced by selective laser melting in the temperature range 20–1200°C is investigated. Metallographic analysis, transmission electron microscopy, and scanning electron microscopy show that structural changes in the alloy begin at 600-700°C and are fully completed at ~1150°C. Differential scanning calorimetry of the alloy with a cellular structure reveals three exothermic processes occurring upon annealing within the temperature ranges 450–650, 800–1000, and 1050–1200°

Genetic diversity of the Central European wild boar (Sus scrofa scrofa) population and domestic pig (Sus scrofa domesticus) breeds based on a microsatellite DNA locus

The results of studies of the genetic structure of the Central European wild boar (Sus scrofa scrofa) population and four breeds of domestic pigs (Duroc, Yorkshire, Large White and Landrace) bred in the Central Black Earth region of Russia are presented in this work. Based on 12 microsatellite loci, a significant ( p <0.05) decrease in the level of genetic variability in bred breeds was shown. The expected heterozygosity and Shannon index were as follows: in the wild boar, Ho = 0.763 ± 0.026, I = 1.717 ± 0.091; in the Duroc breed, Ho = 0.569 ± 0.068, I = 1.191 ± 0.157; in the Landrace, Ho = 0.618 ± 0.062, I = 1.201 ± 0.147; in the Large White, Ho = 0.680 ± 0.029, I = 1.362 ± 0.074; and in the Yorkshire, Ho = 0.642 ± 0.065, I = 1.287 ± 0.156. The results of checking genotypic Hardy–Weinberg equilibrium based on the G-test of maximum likelihood demonstrated that the overwhelming majority of loci in the wild boar population were in the state of said equilibrium. By contrast, in pig breed populations, some loci demonstrated a significant deviation from the indicated equilibrium. In addition, the Yorkshire, Large White, and Landrace populations had loci, for which the hypothesis of neutrality was reliably rejected based on the results of the Ewens–Watterson test. The revealed private alleles, characteristic of the wild boar and breeds, can later be used to identify them. The ordination of the centroids of different herds in the space of the first two principal coordinates based on the matrix of pairwise estimates of Nei’s genetic distances showed that the most distant populations are the Duroc and Boar breeds, and the most genetically close are the Yorkshire and Landrace breeds. The closest to the wild boar population was the Large White breed. The assessment of the effective size, carried out using the method based on the linkage disequilibrium and the molecular coancestry method, showed that in all studied groups, including the wild boar population, the effective size was less than 100 individuals. The low effective size of the wild boar population (Ne = 21.8, Neb = 4.0) is probably caused by the death and shooting of animals due to Pestis africana suum

Investigating the melt pool properties and thermal effects of multi-laser diode area melting

Diode area melting (DAM) is a new additive manufacturing process that utilises customised architectural arrays of low-power laser diode emitters for high-speed parallel processing of metallic feedstock. The laser diodes operate at shorter laser wavelengths (808 nm) than conventional SLM fibre lasers (1064 nm) theoretically enabling more efficient energy absorption for specific materials. This investigation presents the first work investigating the melt pool properties and thermal effects of the multi-laser DAM process, modelling generated melt pools the unique thermal profiles created along a powder bed during processing. Using this approach process, optimisation can be improved by analysing this thermal temperature distribution, targeting processing conditions that induce full melting for variable powder layer thicknesses. In this work, the developed thermal model simulates the DAM processing of 316L stainless steel and is validated with experimental trials. The simulation indicates that multi-laser DAM methodology can reduce residual stress formation compared to the single point laser scanning methods used during selective laser melting

Resistance of Paramecium Species (Ciliophora, Peniculia) to Salinity of Environment

Summary The salinity resistance and tolerance of 10 species from the genus Paramecium were investigated. The species investigated could be divided into groups in according with their resistance. These groups partly corresponded to the classification of the genus proposed earlier on the basis of morphological features. The ciliates from the"woodruffi" group were more resistant than paramecia from the "aurelia" group. P. bursaria and P. putrinum (the former "putrinum" group) have lower salinity resistance and tolerance than the species from two other groups. P. polycaryum has a salinity resistance and tolerance which corresponded to its "intermediate" position between the "aurelia" and the "woodruffi" groups