Improvement of wear-resistant properties of steel 30Н3MF with additional microalloying

One of the directions of wear resistance improvement is microalloying of improved steels. In the studies conducted, the feasibility of adjusting the composition of steel 30Н3MF was determined by additional microalloying of V + Nb in order to give it wear-resistant properties. Microstructural studies of the experimental alloy were carried out. The microstructure is fairly uniform, represented by a matrix and inclusions. Matrix is represented by doped solution, which includes nickel. It is determined that in a chemically and structurally inhomogeneous ingot, even after heat treatment, structural components will remain. Characteristics such as the amount, morphology and distribution of non-metallic inclusions in the metal matrix are mainly laid at the stage of metal discharge from the steelmaking unit, as well as in the process of deoxidation and modification of steel during its off-furnace treatment.

Corrosion characterization of the experimental alloy Ti-35Nb-7Zr-5Ta by electrochemical techniques

The objective of the present study was to evaluate the corrosion resistance of the experimental alloy Ti-35Nb-7Zr-5Ta, modified by laser beam, in a physiological solution of 0.9% NaCl. This evaluation was carried out by open circuit potential analysis (EOCP), potentiodynamic polarization curves and cyclic polarization curves. The open circuit potential curves show the specimen irradiated by laser beam at 35 Hz presented a more stable and corrosion resistant surface. It was observed in the polarization curves, low current densities in the order of nA /cm2, for all specimen indicating an expected passive behavior for the investigated alloy. The cyclic polarization curves show that for specimen treated with laser, the potential for repassivation (Er) is greater in relation to the potential for corrosion (Ecorr), which indicates greater resistance to corrosion of metal alloys when treated with laser.

Investigation Structure and Properties of Wire From The Alloy of Al-rem System Obtained With The Application of Casting in The Electromagnetic Mold, Combined Rolling-Extruding and Drawing

The paper presents the results of studies of the structure and properties of a wire with a diameter of 0.5 mm from an alloy of the Al-REM system with a rare-earth metal content of 7-9%. Wire obtained as a result of the implementation of the technology of its manufacture using the methods of casting into an electromagnetic mold (EMM), continuous extruding and drawing.The rheological properties of the metal of continuously cast round billets from the experimental alloy obtained using an electromagnetic mold are determined. The modeling and analytical assessment of the possibility of carrying out the process of combined rolling-extruding (CRE) of such billets in a closed box-type roll groove of a continuous extruding unit are carried out. The features of metal shaping have been studied. The temperature-speed and technological parameters was found at which the CRE process can be carried out in a stable mode of operation. Data have been obtained for the forces acting on the die and rolls and the moments on the rolls during rolling-extruding.The results of experimental studies of the process of obtaining longish deformed semi-finished products from an experimental alloy on the laboratory unit CRE-200 and the pilot plant unit CRE-400 are presented. The structure of the metal has been studied; data on the ultimate tensile strength, yield strength, relative elongation, and electrical resistivity of hot-extruded rods and wires in cold-worked and annealed states have been obtained.It was found that the proposed processing modes make it possible to obtain by the method of combined rolling-extruding rods with a diameter of 9 mm in industrial conditions from longish billets with a diameter of 18 mm, cast by means of EMM. Wire in a cold-worked and annealed state with a diameter of 0.5 obtained by drawing from the rods with a diameter of 9 mm from an experimental alloy of the Al-REM system containing 7-9 rare earth metals with the required physical and mechanical properties.

Comparative study of superelastic Ti–Zr–Nb and commercial VT6 alloy billets by QForm simulation

A comparative simulation of hot radial shear rolling (RSR) of billets made of a superelastic Ti–Zr–Nb and a commercial VT6 alloy was performed using the QForm finite element modeling program. Rolling in 48 modes with a variable feed angle and elongation ratio at 4 levels and initial rolling temperature at 3 levels was investigated for each alloy. The Ti–Zr–Nb alloy rheology during hot deformation was determined experimentally by hot upset forging and imported into the QForm program. The presence of maxima on the flow curves at the initial stage of deformation, which are absent in the VT6 alloy, is revealed. Simulation results are presented in the form of fields of the stiffness coefficient, strain rate intensity, cumulative strain degree in the maximum reduction section depending on the rolling mode. General regularities of the Ti–Zr–Nb and VT6 behavior in RSR are similar. The gradient of the fields studied decreases, and the roll pressure and torque increase with an increase in the feed angle and elongation ratio. The initial rolling temperature does not significantly affect the deformation pattern, but it significantly affects the roll pressure and torque. At the same time, the experimental alloy demonstrated the greater tendency to localize deforming forces in the near-contact zone and to increase the gradient of stress-strain state parameters over the billet section. The study of the tightening shape and depth of rolled billet ends showed that the Ti–Zr–Nb alloy has a 3.5–9.6 % greater tightening depth. It is shown that experimental alloy rolling requires 1.6–2.4 times higher roll pressure and torque as compared to the commercial alloy.

Effects of Ultrasonic Treatment on the Microstructure and Mechanical Properties of Mg-3Y-3.5Sm-2Zn-0.6Zr (wt %) Alloy

Ultrasonic treatment (UST) was applied in the smelting process of Mg-3Y-3.5Sm-2Zn-0.6Zr (wt %) alloy and the microstructure as well as mechanical properties of the experimental alloy were investigated. Results showed that the effect of UST on grain refinement was obvious, and the distribution of the second phases along grain boundary became discontinuous. The width of the grain boundary precipitates decreased after UST. The contents of solute elements within grains increased, and the morphologies of Zr-rich compounds and Y-rich compounds both at grain boundaries and within grains changed after UST. The mechanical properties of the experimental alloy after UST were significantly improved. The ultimate tensile strength (UTS) was 265 MPa, the tensile yield strength (TYS) was 171 MPa, and the elongation (EL) was 11%. The mechanism of UST of the alloy can be attributed to the combined effects of cavitation-induced heterogeneous nucleation and melt convection induced by acoustic streaming, resulting in the refinement of grains and the grain boundary precipitates, which promoted the improvement of mechanical properties.

ІМПЛЕМЕНТАЦІЯ МЕТОДІВ ПОРОШКОВОЇ МЕТАЛУРГІЇ ДО ПРОЦЕСІВ СЕРІЙНОГО ВИРОБНИЦТВА ЖАРОМІЦНИХ ТИТАНОВИХ ЛОПАТОК ГТД

The questions associated with improvement of efficiency of aircrafts and engines manufacture are considered. In the given context when new aircraft engines are developed, the growth of a share of easy materials such as heat resistant titanium alloys is observed. This is explained by successful complex of physical-mechanical properties, where the mechanical properties to weight ratio is the principal ones. It is noticed, that serial production’s technology of such alloys has high power inputs (double vacuum arc re-melting) and requires a strict composition control of alloying elements, impurities and uniformity of their distribution in the ingot structure. Significant difficulties are attributed to multi-stage deformation processing of large-tonnage ingots from multi-doped titanium alloys, such as ВТ8 alloy. This processing is needed in the operation chain for obtaining the small-sized rod-shaped half-products for production of GTE series blades billets. For elimination the shortcomings of serial technology, such as a large number of operations, the application of the powder metallurgy methods (PM) with technical-economical advantages is offered. The analysis of research results of composition, structure and physical-mechanical properties of an experimental alloy as ВТ8 shows that it is possible to gain the half-finished products of multi-doped titanium alloys with controlled chemical composition after sintering by methods of powder metallurgy. Mechanical properties of such alloy are approximated to serial alloy ВТ8 and thus it is permitted to use the experimental alloy as ВТ8 as constructional material for components which are not subjected to impact and cyclic loadings at the work temperatures like for serial alloy prototype. Received alloy is differed by presence of residual porosity and structure typical for two-phase sintered titanium alloys. For reducing of experimental alloy as-ВТ8 to requirements of the normative documentation (ND) for serial alloy ВТ8 and further implementation, investigation of influence of deformation processing on its structure and mechanical properties was carried out.

Homogenization Treatment to Optimize the Microstructures of the Al-3.5Cu-1.5Li Alloy and Analysis of Al3Zr Precipitates

The microstructure evolution and composition distribution of the cast Al-3.5Cu-1.5Li-0.11Zr alloy during single-step and double-step homogenization were studied with the help of the optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and transmission electron microscopy (TEM) methods. The results show that severe dendrite segregation exists in the experimental alloy. Six different homogenization treatments, conventional one-stage homogenization and double-stage homogenization are carried out, and the best homogenization treatment of the experimental alloys was achieved. Moreover, the precipitation of Al3Zr particles was significantly different after two kinds of homogenization in the experimental alloy. Compared with the single-stage homogenization, a finer particle size and distribution more diffuse of Al3Zr particles can be obtained in the double-stage homogenization treatment.