Effect Of Preliminary Plastic Deformation Research Articles

Результаты исследований релаксации напряжений в стали 25Х17Н2Б-Ш и меди М1 с использованием кольцевых образцов равного сопротивления изгибу

The paper introduces the research into stress relaxation of corrosion-resistant steel 25Kh17N2B-Sh (25Х17Н2Б-Ш) at temperatures of 20 and 100 °C, annealed copper M1 of two types --- soft and subjected to preliminary plastic deformation --- at a temperature of 20 °C, used in the manufacture of parts for butt joints of high-pressure pipelines. The research was carried out on annular samples of equal bending resistance according to the method of Oding. The study shows the action of temperature on the rate of stress relaxation in steel 25Kh17N2B-Sh (25Х17Н2Б-Ш), as well as the effect of preliminary plastic deformation of annealed copper on its relaxation characteristics, which is especially noticeable in the first hours after loading. As a result of the analysis of experimental data and by means of nonlinear regression, we determined the numerical values of the parameters of the equations used to describe the process of stress relaxation. Using the obtained expressions, we calculated and plotted the curves of stress relaxation in the materials under study. Furthermore, we compared the stress values calculated using the obtained relaxation model for steel 25Kh17N2B-Sh (25Х17Н2Б-Ш) at a temperature of 20 °C with the results of stress relaxation of a control sample from the same material, the test results of which were not used in the development of a mathematical model. The calculated data showed good similarity with the experimental data obtained on the test sample, which indicates the correct operation of the mathematical model

Structural Transformations and Tribological Effects in the Surface Layer of Austenitic Chrome-Nickel Steel Initiated by Nanostructuring and Oxidation

Metallography, electron microscopy, and X-ray diffraction are used to study the effect of preliminary plastic deformation in the friction-contact zone on the structural transformations and wear resistance of 12Cr19N9T austenitic stainless steel subjected to subsequent oxidation in air at temperatures of 300–800°C for 1 h. Severe deformation under dry sliding friction produces a two-phase (γ + α) nanocrystalline structure in a ~10-μm-thick surface layer of the steel. The microhardness is 5.2 GPa. Subsequent oxidation at 300–500°C causes an additional increase in the microhardness of the deformed surface layer of steel to the value of 7.0 GPa. This is due to the active saturation of austenite and deformation-induced α'-martensite with oxygen atoms, which rapidly diffuse deep into the metal along the grain boundaries. The oxygen concentration in the surface layer and steel wear products reaches 8.5 wt %. The atoms of the dissolved oxygen efficiently pin dislocations in the γ- and α' phases, increasing the strength and wear resistance of the surface of the 12Cr19N9T steel. Oxidation at 550–800°C results in the formation of a large number of Fe3O4 (magnetite) nanoparticles, which increase the resistance of the steel to thermal softening and its wear resistance.

On the mechanism of the effect of plastic deformation on the corrosion resistance of high-strength cast iron

The mechanism of the effect of preliminary plastic deformation on the corrosion resistance of high-strength cast iron is analyzed. Based on the experimental results, a scheme of the mechanism considering the contribution of the variation in the number and shape of graphite inclusions to the anisotropy of corrosion rate of strained cast iron is proposed.

Effect of preliminary plastic deformation on the structure and physicomechanical properties of aging invar alloy N30K10T3

The invar alloy N30K10T3 after water quenching from 1150°C (austenite, γ phase) has the temperature of the start of martensitic transformation M s ≈ −80°C and the Curie temperature T C ≈ 200°C. The effect of aging-induced phase decomposition in a deformed supersaturated solid solution on its hardness HV, electrical conductivity σ, magnetic permeability μ, and linear expansion coefficient β has been studied. It has been shown that cold plastic deformation of the alloy (at 20°C) to 30–50% increases its hardness, virtually does not change the conductivity, and decreases permeability. Aging of the deformed invar results in increasing HV and σ and decreasing μ. At room temperature, the deformed invar has a low linear expansion coefficient; its magnitude grows the faster, the greater the aging temperature T a. Plastic deformation increases the density of dislocations, which form a banded substructure in austenitic grains. Besides, a metastable martensitic phase has been observed, which undergoes a reverse martensitic transformation into austenite upon heating in the temperature range from 550°C to 650°C. This transformation causes a decrease in the linear expansion coefficient β(T) of the deformed material. In samples aged at T a = 700°C (after deformation), an athermal aging-induced martensite (αa phase) appears after cooling them to 20°C. The appearance of the αa phase is due to an increase in the temperature of the start of the martensitic transformation to above the room temperature caused by aging. In the samples containing the αa phase, there is observed a decrease in β in the temperature range from 350 to 670°C, which is due to the reverse transformation of the aging-induced martensite into austenite (αa → γ).

Low-temperature nitriding of austenitic steel in a vibrofluidized bed

The prospects for use of a vibrofluidized bed (VFB) for low-temperature nitrogen saturation of high-strength austenitic steel based on Cr−Ni−Mn (12Kh17N8G2S2MF) are considered. The positive effect of preliminary plastic deformation on the intensity of nitriding is described. The temperature and time parameters of nitriding in a VFB for strain-aging austenitic steel 12Kh17N8G2S2MF are shown to be adequate for the regimes of the final heat-treatment operation of aging. This creates the possibility of combining the operations of surface alloying and strain aging into a single cycle. This combined treatment increases substantially the resistance of the steel to cyclic loads while preserving the strength parameters. It is shown that the presented method of low-temperature nitriding in a VFB is expedient for improving the service characteristics of austenitic steel 12Kh17N8G2S2MF used for production of force springs of automobile brake systems.

Analysis of certain problems of the brittle fracture of bcc metals

A physicomechanical analysis is made of the conditions under which brittle fracture occurs in bcc metals. A criterion of brittle fracture is formulated on the basis of a quantitative description of the nucleation, starting, and propagation of microscopic cleavage cracks in a substructure that undergoes alteration in the course of deformation. A theoretical analysis is made of the effect of microstresses and the deformational substructure of the material on the critical stress for brittle fracture, and the propagation of brittle microcracks within the substructure is studied experimentally. An examination is made of the general laws that govern the effect of preliminary plastic deformation on the parameters in the brittle fracture criterion and on the fracture toughness of the material.

Effect of preliminary plastic deformation on the destruction of composite material

Effect of preliminary plastic deformation on the destruction of composite material

Study of the effect of preliminary plastic deformation on the mechanical properties and microstructure of structural steel

1. We studied the effect of preliminary plastic deformation on the mechanical characteristics of steel 15Kh2MFA, with σ0.2=950 MPa and 540 MPa, in short-term tension. 2. It was established that different fracture mechanisms exist in steel 15Kh2MFA, depending on the strength (yield point). In the first stage of plastic deformation of smooth specimens of steels 15Kh2MFA (I) and 15Kh2MFA (II), microscopic pores are formed and grow in the direction of the action of the force. Subsequently, along with an increase in pore size in the longitudinal direction, in steel 15Kh2MFA (I) there is also an increase in size in the transverse direction and coalescence of pores. The latter is responsible for the occurrence of a dimpled fracture. In steel 15Kh2MFA (II), the direction of pore growth and coalescence remains lengthwise up to the formation of microcracks and longitudinal lamination at the stage preceding specimen fracture. In this case, the fracture is usually brittle and occurs along the grain boundaries. 3. The last stage of fracture is characterized by rapid pore growth and coalescence and microcrack formation. The fracture criterion which is independent of the degree of preliminary plastic deformation is the technical cohesive strength.

Effect of preliminary plastic deformation on the mechanical properties of austenitic steel at low temperatures

Effect of preliminary plastic deformation on the mechanical properties of austenitic steel at low temperatures

Effect of preliminary plastic deformation on the low-temperature strength of carbon steels

1. We examined the laws governing the development of microheterogeneous plastic deformation in elements of the structure of an alloy during warm and cold deformation. Analysis of the dispersion criteria of microheterogeneous deformation, the distribution density, and the parameter of the deformational stability of the structure revealed constant values after preliminary warm deformation. 2. The change to low-temperature deformation is based on the inheritance of the basic mechanism of microheterogeneous plastic deformation characteristic of preliminary warm deformation, in which the memory of the prior loading by the material is also apparent, determining the direct superposition of warm strain hardening on the low-temperature strength. 3. The increase in the strength of a polycrystalline substance due to the change to low-temperature is almost independent of preliminary warm plastic deformation.

Effect of preliminary plastic deformation in changes in shape of limiting-state curves

Effect of preliminary plastic deformation in changes in shape of limiting-state curves

The effect of preliminary plastic deformation and aging on the brittleness of low-carbon steel

The effect of preliminary plastic deformation and aging on the brittleness of low-carbon steel

Effect of preliminary plastic deformation on fatigue strength of titanium alloy VTZ-1

Effect of preliminary plastic deformation on fatigue strength of titanium alloy VTZ-1

Effect of preliminary plastic deformation on the resistance of materials to the dynamic action of liquid lead

Effect of preliminary plastic deformation on the resistance of materials to the dynamic action of liquid lead

The effect of preliminary plastic deformation upon the resistance of steel to hydrogen embrittlement

The effect of preliminary plastic deformation upon the resistance of steel to hydrogen embrittlement