Key Engineering Materials Vol. 743

Abstract: This paper introduces a new concept of coated fine carbides modified by nanoparticles Al₂O₃, ZrO₂ (inhibitors) as the starting method for improved hardmetals. The study involved computational and experimental methods to determine functional relationships between the parameters of microstructure, sizes, volume content of additives of nanoparticles and properties (transverse rupture toughness, hardness, fracture toughness) of the heterophase hardmetal composites. Factors having a positive influence on the structure of hardmetals are the decrease in the average size and contiguity of carbide grains due to SPS-consolidation and ultrasonic activation during mixing. The study of microstructural parameters by scanning electron microscopy in a combination with x-ray phase analysis indicates high statistical homogeneity of the relative distribution of nanoparticles (inhibitors) in the cobalt binder between carbide grains and the formation of nanostructured inclusions in hardmetal composites.

Abstract: Porosity, values of nanohardness and Young’s modulus of the specimens obtained with the method of selective laser melting were measured with optical methods, scanning electron microscopy and Nano Hardness Tester NHT-S-AX-000X device for measuring physicomechanical properties. Ti-45wt%Nb powder obtained with mechanical alloying was used for selective laser melting. The results have shown that increased heat input due to the laser power growth up to 80 W and scanning speed decrease down to 40 mm/s decreases the porosity of the specimen. The nanohardness average value is not sensitive to the changes of scanning modes in the investigated range. The Young’s modulus decreases with energy input increase.

Abstract: The article deals with the investigation of structure and magnetic properties of plastically deformed Ni₅₁Ti₄₉ alloy. The magnetic hysteresis loops confirm the presence of ferromagnetic properties in the alloy. The transmission electron microscopy (TEM) detects the appearance of lenticular crystals with bending contours which indicate the large distortion of the crystal lattice. The crystal lattice curvature occurs due to the large atom displacement. As a result, icosahedral clusters with the Frank-Kasper (FK) structure can be formed. The spin-polarized density of electron states and the magnetic moments for both non-deformed (near-spherical structure) and deformed (elongated by 5% along the Z-axis) Ni₇Ti₅ (FK-12), Ni₈Ti₅ (FK-13), and Ni₁₀Ti₆ (FK-16) clusters are calculated for the explanation of possibility of magnetization appearance in Ni₅₁Ti₄₉ alloy. The calculations show the increase in the magnetic moments for the deformed clusters. The calculated spectra demonstrate the high density of electron states near the Fermi level which is a characteristic feature of ferromagnetic alloys.

Abstract: In the present study, a mixture of powders (87.9 at.% Ni, 12 at.% Al, 0.1 at.% B) was used as the initial material to produce sintered Ni₃Al + B alloy. Spark Plasma Sintering (SPS) method was used to compact the powder. The powder mixtures were previously prepared in two ways: mixing the initial powders in a mortar (М1) and mechanical activation (М2). The microstructure was observed using optical microscope (OM). The addition of small amount of boron to the initial mixture of nickel and aluminum improves the density of the sintered Ni₃Al intermetallic compound (98.8%). The results of density, bending and microhardness tests showed, that the provisional three-minute mechanical activation improves almost all properties of the sintered material. The compact obtained by SPS by M2 contributes to the formation of a homogeneous fine-grained structure of the material. It leads to further increase in flexural bending strength up to 2200 MPa. This value is almost 8 times the strength of the intermetallic Ni₃Al stoichiometric composition obtained by SPS.

Abstract: The intermetallic compound tin-copper (Cu-Sn) is widely used in the creation of high-quality bearings, electric conductive lubricants, 3D printers. However, when connecting two metals, the bond between atoms in the lattice becomes covalent or ionic. This leads to the fact that the material becomes more brittle. Additionally, the production of intermetallic compounds is cost-based in terms of both material resources and money. In this paper, the ceramics has been sintered based on the intermetallic copper-tin powders, obtained by plasma dynamic method. The raw powdered materials based on Cu-Sn were obtained using a coaxial magnetoplasma accelerator with copper electrodes by adding the crushed tin into the accelerator. Using X-ray diffractometry (XRD) and transmission electron microscopy (TEM) analyses, the presence of such phases as copper Cu and tin-copper Cu41Sn11 in the obtained material has been confirmed. Further, such-synthesized powdered products were used to obtain bulk samples using the spark plasma sintering technology at various sintering parameters. Images from scanning electron microscope showed a uniform sintering of the product at the sintering temperature of 440 °C under a pressure of 60 MPa. It was found that the sintered intermetallic ceramics has the Vickers hardness equal to 120 Hv. The obtained sample has the lower friction coefficient and the smaller wear area in comparison with the sample, made of pure copper.

Abstract: The comparative experimental study of the effect of various types of heat treatment on the formation of the structure and magnetic properties of welded joints 36NHTYU and 12Cr18Ni10Ti alloys was conducted. It is shown that heat treatment 36NiCrTiAl and 12Cr18Ni10Ti welded joints changes the structural and magnetic properties.

Abstract: This paper reports neutron irradiation induced effects on 08Cr18Ni10Ti austenitic steel, which is one of the structural materials of the IVG.1M research reactor. Chosen samples were stored in the beryllium displacer at two different elevation heights and the radiation dose with fast fluence of 0.4·10¹⁹ n/cm² and 4.3·10¹⁹ n/cm². Thorough material analysis reports changes in hardness values, plasticity and microstructure

Abstract: This method grants effective control of the porosity of the sintering materials and ability to obtain compactly packed samples, where simple pressing is not feasible. Spark plasma sintering is one of the probable methods that could lead to larger energy efficiency in material manufacturing. Upon use of SPS, there is no need to “pre-heat” the material by use of pressure or additional use of connecting agents or components. Manufacture of the components is being finished at the instant. Initial microstructure of the powder is being saved. Besides, with use of analyzing method, it is possible to obtain material of the new type, ones that are have resistance to heat. Use of SPS technology could imply lesser time of sintering for highly packed specimens. Decrease of time implies decrease of microstructural changes as a result of diffusion controlled phase changes. Taking into account what has been mentioned above, choosing the best suitable regime for Ti-Al-Nb proposes a variety of intermetallic junctions and could be used for creation of alloys with different physical-mechanical properties. This study concentrates on optimal regime of obtaining intermetallic junction based on Ti-Al-Nb with use of spark plasma sintering.

Abstract: Approbation results of the method for obtaining of the metallic composite material via dynamic impregnation of the fiber with Al alloy using pulse-magnetic field are presented. Process schemes and factors improving adhesive properties and wetting quality of the fiber with the alloy are shown. Results of experimental investigation of the process and external view of the metallic composite samples are given.