Metal Science and Heat Treatment最新文献

Metal matrix composites based on a Fe – Cr – Mn – Mo alloy obtained by the method of self-propagating high-temperature synthesis in the version of aluminobarothermy are studied. It is shown that the reinforcing particles in the composite are structured conglomerates, in which two regions can be distinguished: central (mainly composed of magnesium oxide) and peripheral (mainly composed of aluminum nitride) ones. Increase in the content of the nonmetallic phase first leads to an increase in the number of similar predominantly single inclusions (at 1.09 – 1.73 wt.% phase), and then they are combined into groups (at 1.90 – 3.38 wt.% phase). The influence of the concentration of the structured conglomerates on the mechanical properties and the wear resistance during dry friction of the composites is determined.

The effect of additional alloying with several rare earth metals in an amount of up to 5 wt.% on the aging kinetics of a high-strength heat-resistant magnesium alloy IMV7-1 of the Mg – Y – Gd – Zr system is studied. Features of influence of the added rare earth metals on the properties of alloy IMV7-1 are determined depending on their atomic number and belonging to the cerium or yttrium group.

The microstructure of a new TiB₂ – Ag metal matrix composite coating deposited by electrical explosion spraying and modified by electron beam treatment is studied using x-ray diffraction analysis and scanning and transmission electron microscopy. It is shown that the phase composition of the coating depends on the deposition mode, and the subsequent electron beam treatment normalizes it. The main phases of the resulting modified coating are Ag, TiB₂ and B₂O. After the electron beam treatment, the microstructure of the coating transforms. The nanostructure of the silver matrix is transformed into a nanocrystalline structure with an average crystal size of tens to hundreds of nanometers.

An improved method is suggested for predicting the fractions of microstructure constituents formed in alloy steels during austempering and one-step quenching-partitioning in the temperature range of martensitic transformation. The temperature dependence of exponent n of the Austin–Rickett equation modeling the kinetics of isothermal bainitic transformation at a temperature below M_s is obtained using dilatometric studies of a number of steels. The developed method also allows for the equilibrium condition of the α- and γ-phases, which characterizes suspension of the bainitic transformation during isothermal holding, as well as the inevitable formation of carbides. The method enhances the adequacy of prediction as compared to the traditional methodology.

Prospects of development of light structural magnesium-based alloys alloyed with rare earth metals are considered. The reasons behind the highest strengthening of magnesium alloys alloyed with some rare earth metals separately or in several combinations are analyzed. The obtained experimental data are compared with published results.

The effects of the stress concentrator, the loading diagram and the corrosive environment on the fatigue properties of a drill pipe from aluminum alloy 1953T1 are studied experimentally. It is revealed that the stress concentrator has an insignificant effect on the fatigue characteristics of 1953T1. The loading diagram is a more significant factor, and bending with torsion has a significantly greater effect then the tension-compression loading scheme. The corrosive environment has the highest impact on the fatigue life of the drill pipe and reduces significantly the fatigue characteristics of aluminum alloy 1953T1, which requires obligatory optimization and control of the chemical composition of the process liquid during operation.

The microstructure and the hardness of bearing ring blanks made of new heat-resistant bearing steel VKS17-ID (a counterpart of M50NiL VIM-VAR) are studied after various hot pressure treatments and subsequent annealing. The regularities of the influence of the processing on the structure and properties of the steel are determined. The results obtained may be used to develop and optimize the processes of forging and annealing in the industrial production of bearings from steel VKS17-ID.

The structure and phase composition of samples of a Ti – 6Al – 4V alloy obtained using an EOSINT 280M laser printer are studied using scanning and transmission electron microscopy after cyclic three-point bending tests at room temperature. The features of the deformation process during bending of the samples are considered. It is shown that, in contrast to the cast alloy that fractures by a brittle mechanism, the Ti – 6Al – 4V alloy produced by laser 3D printing undergoes brittle-ductile fracture under the conditions of cyclic bending deformation, which is associated with formation of new pores in the deformed alloy.

Experimental data in the field of structural strengthening of aluminum alloys, obtained in recent years and confirming the views and foresight of a prominent Russian scientist V. I. Dobatkin about the possibility of expanding the industrial use of structurally hardened materials are considered. Examples of the development and industrial application of new aluminum alloys are given. The features of structural strengthening of aluminum alloys of two classes (heat hardenable and not heat hardenable) are analyzed.

Al – Ni – Fe coatings on steel 35 deposited by the electrospark method using a non-localized electrode and mixtures of nickel and aluminum granules are studied. The kinetics of the mass transfer of mixtures of granules of three compositions during application of the coatings is investigated. The phase composition, the microstructure and the hardness of the coatings are determined. Corrosion and wear tests are carried out. It is shown that the deposition of Al – Ni – Fe coatings on the steel can reduce its susceptibility to spontaneous corrosion, lower the corrosion current density by a factor of 1.6 – 2.6, raise the wear resistance by a factor of 3.7 – 6.2 and elevate the heat resistance.