International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

To create a high-hardness and wear-resistant coating on the heat-resistant aluminum AK4 alloy, the technology of microarc oxidation is used. The possibility of forming an oxide layer on the surface (mainly of α−Al2O3 and γ−Al2O3 phases) with a thickness of about 150 μm and a hardness of 17000 – 18000 MPa is shown. For this, the process of microarc oxidation was carried out at a current density of 20 A/dm2 in an electrolyte of the composition KOH (1-2 g/L) and Na2SiO3 (6-12 g/L). The obtained properties of MAO coatings on the AK4 alloy make it possible to effectively use such materials for engine elements.

Sn-Ag powder alloy of eutectic composition is demanded in the production of powders for soldering pastes used in electronics. Non-eutectic alloy has found its application in catalysis for CO2 reduction, in 3D printing, as the promising material for lithium ion batteries. In this work the way of synthesis of Sn–Ag nanostructured powder alloy with near-eutectic composition based of cementation reaction in the system Sn0/Ag+ in aqueous solutions was proposed. The peculiarities of alloy powder synthesis in acid and slightly acid solutions were studied. Factors influencing on powder microstructure, phase and elemental composition were identified. Electrochemical behavior of tin in aqueous solutions for silver deposition was studied by potentiometric method.

Powder high-entropy alloys (HEA) of TiCrFeNiC equioatomic composition were synthesized by hot forging (HF). The phase composition and parameters of the fine structure of the alloys are determined. It is shown that at all annealing temperatures of the alloys their phase composition does not change significantly and consists of two solid solutions of substitution – FCC and BCC and two carbide phases – TiC and Cr3C2. The mechanical properties of the alloys are at a rather high level – so the maximum strength of the alloy was 2243 MPa and the hardness is more than 62 HRC, which can be explained by the effect of high entropy and in situ synthesis of carbides in the manufacture of alloys.

The low-temperature method of Sn–Ni–Zn powders synthesis by cementation of tin and nickel with zinc powder from acidic solutions with the formation of “zinc core – porous nickel shell – external tin layer” structures has been proposed. The method provides metals ratio control in wide ranges (7–41 at. % of tin, 38–86 at. % of nickel and 7–24 at. % of zinc) by variation of the process duration. X-ray phase analysis data give evidence on the presence of β-Sn and Zn phases as well as NiZn3 and NiSn intermetallics in the powders obtained. Differential scanning calorimetry data show the availability of Sn–Zn eutectic with the melting point at 171.2 °C in the powders with high tin content (30–40 at. %). The formation of the ternary intermetallic τ1 phase (Ni3+xSn4Zn) has been established to occur as a result of the powders heating at 260 °C. The discovered low-temperature phase transformation in Sn–Ni–Zn system at 260 °C is of interest for electronic equipment assembly processes that include consecutive stages of soldering and resoldering.

Equiatomic alloys TiCrFeNiCuC were made by two methods of powder metallurgy – vacuum sintering and hot forging followed by annealing. In the process of sintering the TiCrFeNiCuC blanks, the influence of entropy of mixing resulted in the formation of solid substitution solutions mainly on the basis of the FCC lattice, and also formed titanium carbide (TiC0.74). In samples obtained by hot forging and subsequent annealing, two carbides TiC and Cr3C2 were found, and titanium carbide being formed with lower carbon content (TiC0.58). In addition, the forged samples showed significantly higher values of the defect of the crystalline structure, which leads to increase in their hardness.

The possibility of control of efficiency of different factors of high voltage electric discharge (HVED) impact on Ti – Al – С powders system for aimed synthesis of dispersion-hardening components is shown. Nanolaminate-composite Ti₃AlC₂ – TiC with hardness of HV5 = 7 GPa, obtained by consolidation of blend of 85 % Ti + 15 % Al initial composition after HVED with the use of multi-point electrode system has needle structure of Ti₃AlC₂ (a = 0.3068 nm, c = 1.844 nm) with size up to 10 μm, and TiC dispersion-hardening phase (a = c = 4.4331 nm) with particle size no more than 1 μm is situated between grains of Ti₃AlC₂. Dynamic strength of specimens depending on electrode system used during HVED treatment of blend variated in range from 160 to 620 MPa, Young modulus – from 13 to 22 GPa at deformation rate from 600 to 900 s–1. Material has high levels of heat resistance, relative change of mass is no more, than 0.001.

Quantitative analysis of the phase composition of the Ti-Al-V-Mo-Zr system alloys was carried out during operation using the Thermo-Calc program (TCW5 version, TTTI3 database). Polythermal and isothermal cuts are plotted, design temperature values of liquidus, solidus and transition into β-field during heating are given. Regarding the titanium alloy of the Ti-Al-V-Mo-Zr system the effect of annealing temperature on the microstructure of the alloy as well as on the alloying elements content in α and β–phases was studied using the scanning electron microscopy method.

Quantitative analysis of the phase composition of the Ti-Al-V-Mo-Zr system alloys was carried out during operation using the Thermo-Calc program (TCW5 version, TTTI3 database). Polythermal and isothermal cuts are plotted, design temperature values of liquidus, solidus and transition into β-field during heating are given. Regarding the titanium alloy of the Ti-Al-V-Mo-Zr system the effect of annealing temperature on the microstructure of the alloy as well as on the alloying elements content in α and β–phases was studied using the scanning electron microscopy method.

Changes of dispersity, form factor and phase composition of powder mixtures of 75% Ti + 25% Al, 50% Ti + 50% Al, and 25% Ti + 75% Al mass compositions after treatment by high voltage electric discharge in kerosene are experimentally studied. Regularities of their dispersion and synthesis of TiC, AlTi₃, AlTi, Al₂Ti, Al₃Ti, double carbide Ti₃AlC, МАХ-phases Ti₃AlC₂ and Ti₂AlC, Lonsdaleite are found.

This study reports the structural evolution of equiatomic AlCuNiFeTi high-entropy alloy (HEA) from elemental materials to solid solution during mechanical alloying (MA), and further, to equilibrium phases during subsequent thermal annealing. It was justified experimentally that MA of Al-Cu-Ni-Fe-Ti powder mixture during 15 hours resulted in a single-phase nanocrystalline HEA with a structure of ВCC solid solution. During thermal annealing recovery and recrystallization of the BCC solid solution take place at temperatures ranging from 130 to 650 °C, and phase transformation, and grain growth of equilibrium phases occur at higher temperatures. The phase composition transforms to BCC and FCC solid solutions when the MA powder was annealed at 700 °C for 1 h. The BCC and FCC solid solution structure can be maintained even after the alloy was annealed at 1000 °C. The alloy powder was consolidated by pressure sintering at 800 °C with 5 GPa pressure for half an hour. The sintered sample exhibits 10.7±0.3 GPa in Vickers hardness.