Volume 59, Nº 5-6 (2017)

The substructure and microstructure of pearlite in hypoeutectoid low-carbon steel 09G2S is studied using high-contrast images in a scanning electron microscope and electron backscattered diffraction. Acorrelation is established between local deviations from “ideality” in the structure of pearlite and the substructure of pearlitic ferrite. Fragments of pearlitic ferrite, whose development is connected with propagation of long-range misorientations, are seen. It is shown on the basis of visualization that the single-crystal matrix of the pearlitic ferrite consists of individual fragments. These fragments are not generally flat.

Conditions are analyzed for implementation of helical extrusion of iron-nickel alloy billets with the aim of forming a submicrocrystalline structure within them. Properties are provided for heat-resistant iron-nickel alloys ÉP718-ID (KhN45MVTYuBR ID) and Inconel 718. Two alternative versions are considered for deformation of this type at high and low temperatures. A regime is suggested for helical extrusion of small billets.

Eutectoid steel AISI 1080 is studied after annealing at 850°C and thermal cycling treatment (TCT) that involves heating at a rate of 10 K/min to 775°C, holding for 10 min, and cooling at a rate of 95 K/min. An increase is established in the content of cementite precipitating over austenite grain boundaries, and relative elongation with retention of yield and ultimate strengths with an increase in number of TCT cycles. After five cycles relative elongation reaches 29% with ultimate strength of 670 MPa.

The possibility of using micro-arc chemical heat treatment in bituminous coal powder for simultaneous impregnation of a steel surface with carbon and carbide-forming elements, i.e., chromium and molybdenum, is studied. Chemical and phase compositions of the diffusion layers are determined. Formation of carbide coatings based on these elements is confirmed.

High-strength bainitic cast iron is studied after isothermal hardening at 340°C for from 0.5 to 5 h with the use of a non-destructive eddy-current method for monitoring the microstructure and mechanical properties. Iron microstructure is studied by optical microscopy and x-ray diffraction analysis. Brinell hardness and the impact energy are determined. Correlation is established between electromagnetic sensor signal, microstructure, and mechanical properties. It is shown that induced voltage and normalized impedance may be used for non-destructive monitoring of the production process and cast iron quality.

The microstructure, mechanical properties and superplasticity indices of sheets of aluminum alloy Al – 3% Mg with 0.3% Zr and 0.1% Ti are studied. Use of low-temperature homogenizing (at 360°C) and two-stage hot rolling (at 360 and 420°C) with intermediate annealing at 420°C (3 h) provides quite good thermal stability of alloy grain structure and improved strength properties at room temperature. The alloy exhibits signs of superplasticity with a constant deformation rate of 5 × 10^–3 sec^–1 and retains a virtually unrecrystallized structure after 200% deformation.

Ingot chemical composition and the mechanical properties of semiproducts produced at various Russian enterprises from 1971 to 2011 are analyzed. The fundamental possibility is demonstrated for predicting probable values of mechanical properties of wrought titanium alloy semiproducts using industrial monitoring data with errors determined by the contemporary level of industrial production.

Methods and procedures are discussed for more economic and effective use of scandium for alloying aluminum alloys. Specifically, it is recommended to introduce scandium and zirconium into aluminum alloys in a 1 : 1 ratio instead of the usual 3 : 1 with the same overall element content. It is also suggested that microalloying with scandium in an amount of 0.1% instead of 0.22% provides the required level of properties in many cases. The possibility of refining the structure of the Al – 2% Sc master alloy for increasing its adaptability (assimilation by the aluminum melt) due to an increase in crystallization rate during ingot casting and other procedures is considered.

The effect of heat treatment regimes on hardness, impact strength, and wear resistance of rail steel for high-speed tracks (rail quality category R350HT) is studied. Analysis of steel properties with a different structure is compared: pearlitic, and upper and lower bainite. It is shown that the steel with bainitic structure has the best impact strength, but wear resistance is better for steel with a lower bainite structure.

The structure of coatings deposited on steel 45 by plasma-powder surfacing of white wear-resistant cast iron is studied. The effects of surfacing regime and additional production effects on the welding bath during surfacing produced by current modulation, accelerated cooling of the deposited beads by blowing with air, and accelerated cooling of the substrate with running water on the structure, are determined. A new composition is suggested for powder material for depositing wear-resistant and corrosion-resistant coatings on a carbon steel by the plasma-powder process.

Comparative analysis of results of contact wear of steels Kh12M and R6M5 is performed with allowance for the structural evolution detected in experimental studies and by computer modeling. It is shown that metal matrix properties determine steel resistance to contact wear and the structural changes arising during wear.

The effect of the chemical composition of alloys of the Sn – Cu – Co system used as a binder for diamond abrasive tools on their structure and hardness is studied. It is shown that in the range of concentrations of the elements studied alloy structure is represented by three phases, i.e., β-Co, a solid solution of tin and cobalt in copper (Cu), and an ε (Cu₃Sn) intermetallic phase. The lowest microhardness of the three phases is exhibited by β-Co, as a result of which with an increase in cobalt content alloy macrohardness decreases.

The effect of boron additions on the properties and structure of rolling mill iron is studied. The composition of boride phase and carbides, and also the ratio of structural components in iron with different boron contents are determined. Structural transformations in iron during heat treatment are studied by differential thermal analysis and differential scanning calorimetry. The optimum concentration of boron in iron for improving its properties is determined.

The effect of microstructure on the special features of the occurrence of shape change in alloy based on titanium nickelide displaying shape memory and superelasticity is studied. It is shown that total realization of these effects depends not only on alloy structure but also on deformation temperature. Temperature dependences are established for critical strains and stresses governing conditions for total initial shape recovery.