L. N. Ignatenko

Band structure and packet-martensite structure. Comparison of evolution paths

We consider the similarities and differences between the band substructure and the packet-martensite structure in Ni3Fe alloyed with 38KhN3MFA steel. The variation of their quantitative characteristics with strain and with initial polycrystal grain size is analyzed. The main factors governing the morphological features and the behavior of the considered structures are found to be the laws governing the evolution of the dislocation-disclination ensemble.

Influence of the Substructure Type on the Carbon Redistribution in Martensitic Steel in the Course of Plastic Deformation

The phase and structure transformation of tempered martensitic steel in the course of plastic deformation is considered in the present paper. A close correlation between the evolution of the substructure type and the behavior of carbon is established. The carbon concentrations in solid solution and on crystalline defects of the material as a whole and in different dislocation substructures are investigated versus the degree of plastic strain.

Structure and Phase Content of a Weld in Fe–0.09C–2Mn–1Si Steel

The structure and phase content of a weld in Fe–0.09C–2Mn–1Si steel are investigated by the methods of transmission electron microscopy (TEM) and metallography. A gradient weld structure is established. The manner in which the phase content of steel, the ferrite and pearlite grain sizes, and the morphology of cementite particles depend on the increasing distance from the weld center is elucidated.

Electron Diffraction Analysis of the Fracture Zone of Fe–0.45C–17Mn–3Al Steel Subjected to Multicyclic Fatigue Tests

The methods of transmission electron microscopy are used to investigate the structure and phase content of Fe–0.45C–17Mn–3Al steel subjected to multicyclic fatigue tests to failure after intermediate electrostimulation. It is demonstrated that electrostimulation does not change the mechanism of steel failure. An increase in the operating life time of samples after electrostimulation in the intermediate test stage is connected with the hindered γ → ε-martensitic transformation, the relaxation of stress concentrators, and the reduction of the volume fraction of the critical dislocation (network) substructure in which ε-martensite is mainly developed.

Substructural phase transitions during intense plastic deformation of low-carbon ferrite-perlite steel

We have studied the evolution of the defect structure and phase composition of low-carbon ferrite-perlite steel subjected to intense plastic deformation using diffraction electron microscopy. It has been shown that a high degree of deformation is accompanied by disruption of the perlite columns. We have found and described two perlite decay mechanisms: decay of the carbide plates by a path of their granulation due to dislocation slip and dissolution of cementite arising from the outflow of carbon atoms from the carbide phase into ferrite crystal lattice defects. We have described the phenomenon of morphological reconstruction of the cementite-phase particles (a transition from layers to spheres) under plastic deformation conditions.

Anomalous mass transfer and phase and structural changes in ?-Fe when acted upon with electron pulses

The phase composition and the defect structure of armco-iron irradiated with a relativistic electron beam is investigated using electron microscopy and x-ray structural analysis. Specimens with a chromium coating and without it were irradiated.

Effect of rapid thermocyclic tempering on substructure, phase composition, and the initiation of fracture in a martensitic steel

The method of electron microscopy is used to study the fine structure of martensitic steel 17Kh4N2M2VF when subjected to rapid thermocyclic tempering. It is found that substructural and phase transformations take place in martensite due to repeated rapid temperature changes within the range 20–700°C. The phase transformations involve the decomposition of cementite and residual austenite and the formation of special carbides. The substructural changes are connected with fragmentation of the material. The density of high-angle fragment boundaries increases near the specimen surface along with scalar and excess dislocation density. The phase structural transformations entail the formation of long-range stress fields, the local relaxation of which leads to the development of microcracks and fracture of the material.

Laws of substructural and phase transformations in the plastic deformation of martensitic steel

Substructural and phase transformations in the course of plastic deformation in tempered 34KhN3MFA steel are considered. A relation is established between the type of substructure and the phase state of carbon. A direct relation is established between the carbon content in the solid solution and the crystal-lattice distortion. The carbon concentration at dislocations and fragment boundaries is determined.

Fragmented substructure and crack formation in low-alloy steel

In the work we studied the substructure of 30KhGSA steel after rolling. A relation has been established between the macrofracture of the specimen and its dislocation substructure. The formation and completion of a fragmented substructure with precipitation of carbides at the junctions of fragments during rolling indicate that the lifetime is close to exhaustion. Annealing that partially or completely destroys the fragmented substructure causes microcracks to collapse and heal, eliminates the microcrack nucleation sites, eliminates trajectories of facilitated microcrack growth, which follow subboundaries, and restores the plasticity of the steel.

Substructural and carbide transformations during plastic deformation in tempered chromium-nickel martensitic steel

The evolution of the defect and carbide subsystems has been studied during the plastic deformation of chromium nickel steel with the structure of tempered martensite. A correlation has been established between the substructural transformation and the change during plastic deformation. The nondislocation shear resistance has been estimated.