V. M. Schastlivtsev

Mechanical properties and fracture upon static tension of the high-carbon steel with different types of pearlite structure

The hardness and mechanical properties of the U10 steel (1.03 wt % C) with pearlite structures that were formed by isothermal decomposition at temperatures of 650°C (coarse-lamellar pearlite) and 500°C (fine-lamellar pearlite) as well as upon subsequent annealing of fine-lamellar pearlite at a temperature of 650°C for 10–300 min have been studied upon tensile tests. Fractures of the steel with different types of pearlite structure have been examined using scanning electron microscopy. The interrelation between the mechanical properties and the structural features and character of fracture has been analyzed for this steel with pearlite structures differing in the dispersity, morphology, and defect structure of cementite, and in the levels of solid-solution strengthening and microdistortions of the ferrite-constituent lattice.

Peculiarity of structure and crystallography of plastic deformation of lath martensite in structural steels

Abstract The structure of a martensite packet and cold plastic deformation within one packet, as occurring in the quenched of pseudosingle crystals of 15CrNi4 and 37CrNi3 structural steels, was studied by X-ray diffraction, scanning electron microscopy, and optical microscopy. By electron microscopic analysis it is shown that there are six variants of martensite crystals throughout the packet, in agreement with previous X-ray crystallographic results on the number of martensitic variants in a packet. The slip planes in pseudosingle crystals were found to be close to {112} M and {110} M , which are typical of the bcc lattice.

Phase transformations in Ni-Mn-In-based alloys in magnetic field

The effect of a high-strength magnetic field on the phase transformations of ferromagnetic materials based on the Ni-Mn-In system with different degrees of alloying has been revealed experimentally. The effect of the chemical composition of the alloys and magnetic treatment on the martensitic transformations and magnetic transitions has been investigated. It has been established that, upon substituting nickel atoms with manganese atoms, the temperature of the martensitic transformation decreases.

Structural features of the behavior of a high-carbon pearlitic steel upon cyclic loading

The structural evolution upon high-cycle fatigue (tension with the magnitude of stress in a cycle below the macroscopic yield stress) of the hypereutectoid steel U10 (1.03 wt % C), in which pearlite of different morphology (fine-lamellar, coarse-lamellar, and partially spheroidized pearlite) was formed, has been investigated by scanning and transmission electron microscopy. Based on the fractographic analysis, features of fracture of these structural states have been considered. At a significant distance (10 mm) from the fatigue fracture, features of structural transformations caused by cyclic loading have been revealed. It has been shown that upon high-cycle fatigue in the steel U10 with structures of lamellar and partially spheroidized pearlite, substantial structural changes occur, namely, fragmentation and partial dissolution of cementite plates, and in fine pearlite, additionally, spheroidizing of cementite and polygonization of the ferritic component are observed. A dependence of the character of fracture on the type of structure formed upon fatigue loading has been established. In the steel with a nonequilibrium structure of unannealed fine pearlite, an enhanced elasticity modulus, as compared to other more stable structures (coarse-lamellar, annealed fine, and spheroidized pearlite), and a reduction in the magnitude of the elasticity modulus under the action of cyclic loading have been found. It has been established that the structural changes in fine pearlite of laboratory specimens of the steel U10 upon cyclic tension are qualitatively similar to those in a railroad wheel of the steel 65G under the service conditions.

Martensitic and Magnetic Transformations in Ni-Mn-In Alloys

Dilatometry, magnetometry, and optical metallography were used to study structural and magnetic transformations in Ni-Mn-In alloys of different compositions. Temperatures of structural and magnetic transformations of the Ni47 − xMn42 + xIn11 alloys (with x = 0–2) were determined. It is shown that, as the valence electron concentration decreases, the martensitic transformation temperature decreases. Some of the Ni-Mn-In alloys exhibit a ferromagnetic transformation in both the initial austenite and in the arising martensite.

Magnetic-field-induced martensitic transformations in Ni47 − x Mn42 + x In11 alloys (with 0 ≤ x ≤ 2)

Magnetic properties and martensitic transformations in the Ni47 − xMn42 + xIn11 alloys (with 0 ≤ x ≤ 2) have been studied. The magnetic-field-induced martensitic transformation was found to be observed for all the alloys. The critical temperatures of magnetic and structural phase transformations, temperature dependences of spontaneous magnetization of austenite and martensite, and the critical field, at which the martensitic transformation occurs, have been determined based on magnetic measurements performed for the alloys under study. The spontaneous magnetization of the alloys in the martensitic state has been shown to be lower than that in the magnetic-field-induced austenitic state by a factor of six.

Effect of austenite-decomposition temperature on bainite morphology and properties of low-carbon steel after thermomechanical treatment

Peculiarities of the bainite structure formed in low-carbon steel 07G2NDMBT during isothermal austenite decomposition, namely, the sizes of crystallites, their mutual orientation, and the presence of cementite precipitates, are considered. The temperature range of the formation of bainite with the subgrain structure was determined. The size of the austenite grain and degree of hot deformation were found to affect the transformation of bainite that occurs upon subsequent cooling and the submicrocrystalline bainite structure. We studied the structure and mechanical properties of a rolled sheet 16 mm thick, which was subjected to thermomechanical treatment (TMT) under plant conditions in accordance with optimum regimes. It was shown that the high structure dispersion of the steel subjected to TMT is due to not only the formation of bainite with the subgrain structure, but also the partial transfer of crystal-structure defects from hot-rolled austenite to the final bainite structure.

Microstructure and properties of low-carbon weld steel after thermomechanical strengthening

Optical metallography and transmission electron microscopy have been used to study the structure of the rolled sheets produced from the pipe steel of Kh90 class. The sheets were manufactured using different technological schemes of strengthening: direct quenching from rolling heating (QRH) followed by high-temperature tempering; and two-step thermomechanical treatment with rapid cooling to a desired temperature (TMT). A relationship between the nature of the structure and mechanical properties of the rolled sheet has been established. It has been shown that the two-step thermomechanical treatment has significant advantages over the quenching from the rolling heating, which is related to the formation of highly dispersed bainite with a subgrain structure upon TMT.

Effect of thermomechanical treatment on the resistance of low-carbon low-alloy steel to brittle fracture

Structure and mechanical properties of rolled plates (20–35 mm thick) of low-carbon low-alloy steel subjected to thermomechanical treatment (TMT) according to various regimes under laboratory and industrial conditions have been studied. Structural factors that favor obtaining high mechanical properties have been established. The retarding action of TMT on softening upon tempering has been revealed. The reasons for the decrease in the resistance to brittle fracture of the steel subjected to TMT, repeated quenching from the temperature of the furnace heating, and tempering have been determined.

Possibilities of Nondestructive Testing of Physico-Mechanical Characteristics of Hypereutectoid Carbon Steels with the Structures of Isothermal Austenite Decomposition

The possibilities of estimating the hardness, the wear resistance under abrasive action and sliding friction, the impact strength, and the internal stresses of the U9 steel (with 0.94% of carbon) with the initial fine-lamellar pearlite structure annealed at 650°C during 2–600 min on the basis of magnetic and electrical characteristics, readings of an eddy-current instrument, and parameters of electromagnetic-acoustic conversion are studied. A comparative analysis of the magnetic, electromagnetic, strength, and tribological characteristics of the U10 and U15 hypereutectoid steels (with 1% and 1.53% of carbon, respectively) subjected both to isothermal treatment at 330–650°C (with formation of pearlite and bainite structures) and to additional short-time annealing at 650°C is carried out.