A. N. Solonin

Study of the structure and mechanical properties of corrosion-resistant steel with a high concentration of boron at elevated temperatures

Because of the high cost of corrosion-resistant steels, a necessary condition for their production is reducing rejection at all stages of processing, including hot forming, by optimizing process parameters. In this work, the mechanical characteristics of a corrosion-resistant steel with high content of boron have been studied at elevated temperatures. Using a special complex for the physical simulation of thermomechanical processes, it has been shown that the optimum temperature range of hot compressive plastic deformation is 950–1100°C. A mathematical model has been constructed, which relates the yield stress to the parameters of the process of hot plastic deformation. During deformation in the range of 850–1150°C, the boride particles present in the steel become oriented perpendicular to the compression axis; at high temperatures, the spheroidization of titanium diborides occurs, which reduces their size.

Structure and mechanical properties of Ni-Cu-Ti-Zr composite materials with amorphous phase

The structure of specimens of Ni-Cu-Ti-Zr alloys with an amorphous phase has been examined by X-ray diffraction, as well as by transmission and scanning electron microscopy. Mechanical characteristics of the alloys have been determined using universal testing machines. Transformation-induced plasticity has been found to exist. The specimens demonstrate a good combination of strength and plasticity owing to both the composite effect of a heterophase structure and the dynamic martensitic transformation that develops during deformation.

Calculation of the yield point of silumins by the characteristics of their structure

A model is constructed showing the possibility of calculating the yield point by the structural characteristics of alloys of the Al-Si-Cu and Al-Si-Mg systems in natural and artificially aged states. This model possesses good prediction ability at copper concentrations up to 5%, magnesium up to 1%, and silicon up to 11% at an aging temperature of 140–220°C and a holding time of up to 100 h. The maximally possible values of the yield point for the industrial silumins of the systems under consideration are determined.

Simulation of the flow stress of recrystallized single-phase alloys of the Al-Mg and Al-Cu systems

For single-phase recrystallized alloys of the Al-Mg and Al-Cu systems, a model of the dependence of the flow stress on the concentration of the doping element, grain size, and degree of residual deformation is suggested. A physical approach for analysis of the mechanism of alloy strengthening demonstrated a similarity in the dependences of the flow stress in various systems, which permitted developing a universal model for the alloys under consideration. The calculation error is within 6%.

Simulation of flow stress in Al-Mg alloys quenched after casting

Based on an analysis of physical factors of strengthening, a mathematical model of the flow stress of single-phase Al-Mg alloys quenched after casting has been constructed depending on the main structural characteristics (density of dislocations, concentration of alloying elements in the solid solution, and grain size) for the magnesium concentrations of 1.5–9.0 wt %. The parameters of the mathematical model have been corrected based on experimental dependences of the flow stress of Al-Mg alloys with various grain size. The model suggested makes it possible to predict the flow stress with an error of no more than 13%.

Development of Heat-Resistant Aluminum Alloys for Electrical Engineering Purposes Based on the Al – Fe – Si System

The effect of small additions of Mn, Ni, and Cr on a set of mechanical properties at room and elevated temperatures and electrical conductivity of alloys based on the Al – Fe – Si system is studied. It is shown that nickel increases electrical conductivity by 3% for alloys based on the Al – Fe – Si system, and chromium and manganese reduce it by 5 – 10%, which is connected with formation of a more alloyed solid solution. It is established that as a result of cold deformation treatment a dispersed structure forms within the alloy with an average excess phase size up to 0.7 μm. Excess phases of this size are effective recrystallization barriers, and therefore a cold-worked structure is retained in all alloys up to 300°C, which points to good thermal stability of the experimental alloys.

Boron-Containing Steel Structure and Properties at Room and Elevated Temperature

A Gleeble 3800 thermomechanical process physical simulator unit is used to study the structure and mechanical properties of corrosion-resistant steel with a high boron content intended for production of hexagonal pipes for exhausted nuclear fuel storage. Compression tests at room and elevated temperature show that with an increase in test temperature from 20 to 600°C yield strength and flow stress decrease by a factor of two in the steady-state stage, and over the whole test temperature range the steel demonstrates good ductility in compression. The steel’s structure does not undergo marked changes during deformation: stringing, formed during hot forging, is retained during subsequent plastic deformation.

Modeling for the structure evolution of alloys of the Al-Cu-Mg system during natural ageing

Natural ageing in alloys of the Al-Cu and Al-Cu-Mg systems is investigated and modeled. To determine the kinetic parameters, a method for measuring the electrical resistance is applied as the basic method. With the use of the Avrami equation in the differential form, a model for the structure evolution (changes in the volume fraction of the Guinier-Preston zones (GPZs) and the depletion of the solid solution) and the change in the yield strength for the alloys during natural ageing is constructed. In the case of the Al-Cu-Mg ternary system, two types of zones are present (the GPZ and the Guinier-Preston-Bagaryatskii zone (GPBZ)). In this case, the dissociation of the oversaturated solid solution at room temperature is described by a set of differential equations. The accuracy of the constructed model of the dependence of the yield strength on the alloy composition and the natural ageing time is 6%, which is within the error of experimental determination for this parameter.

Modeling the evolution of the structure and properties of alloys for an Al-Zn-Mg system in ageing

An investigation into and modeling of artificial ageing in alloys of an Al-Zn-Mg system are carried out. To determine the kinetic parameters of the dissociation of a supersaturated solid solution, methods of transmission electron microscopy, a measurement of electric resistance at heightened temperature, and differential scanning calorimetry are used. To describe the evolution of the structure in ageing, the Avrami equation and the ageing time dependence of the particle size are applied. A comparison between the computational and experimental values of particle sizes showed the sufficiently high accuracy of the model. Based on this, the yield strength for alloys of the system under consideration in the aged state was computed. The computational error was 11%, which is comparable with the error of the experimental determination of the yield strength.