Abstract—The effect of severe plastic deformation performed in a Bridgman anvils at 77 K on the saturation magnetization, the phase composition, and the crystal geometry characteristics of the phases of a metastable austenitic–martensitic Fe–18Cr–10Ni alloy is investigated. High-pressure (hydrostatic) torsion at a true strain e = 3.4–5.8 at 77 K is found to form two martensitic phases, namely, the ferromagnetic α phase and the paramagnetic ε phase. Mechanisms explaining the nature of changing the saturation magnetization are proposed.

This study consideres application of the digital image correlation method for estimating the relative deformations of composite materials obtained with the use of thermal treatment by laser radiation. The use of this technology made it possible to determine the mechanical properties of materials containing macroscopic austenite regions distributed in the martensite matrix according to a given law. The evolution of strain fields that occur when a load is applied to the samples under study is determined. The influence of the shapes and sizes of regions with high plastic properties (austenite) on the integral mechanical characteristics of composite materials has been studied.

Исследованы механические характеристики композитных материалов на основе сплава Fe – 18 % Cr – 10 % Ni, состоящих из пластичных макроскопических областей аустенита, распределенных в высокопрочной мартенситной матрице. Получены кривые напряжение – деформация для образцов, в которых аустенитные области различаются по размерам и форме. На основе анализа построенных диаграмм определены формы аустенитных областей, оптимальные с точки зрения сочетания прочностных и пластических характеристик материала.

Mechanical characteristics of composite materials based on Fe – 18% Cr – 10% Ni alloy and composed of plastic macroscopic austenite regions distributed in a high-strength martensite matrix are studied. Stress-strain curves are obtained for the specimens with austenite regions differing in size and in shape. The plotted curves are used to determine the shapes of the austenite regions optimal in terms of combining the strength and ductility parameters of the material.

Mechanical characteristics of composite materials based on Fe – 18

The article investigates influence of large plastic deformations created in the Bridgman anvils on the mechanical properties and microstructure of metastable alloys of the iron-chromium-nickel system of the austenitic-martensitic class. It is found that the application of deformation in the Bridgman anvils with a true logarithmic deformation e = 6-7 leads to formation of the α-phase (deformation martensite) with significantly higher mechanical properties compared to martensite formed during deformation by linear rolling. The authors reveal the differences in the microstructure of the alloy after deformation in the Bridgman anvils and deformation by rolling, which explain the discovered effect.

The influence of severe plastic (megaplastic) deformation in a Bridgman anvils on the structure, hardness, and spontaneous magnetization of a metastable Fe–18Cr–10Ni alloy in two initial states, namely, austenitic state after hot plastic deformation and martensitic state after subsequent cold plastic deformation, is investigated. High-pressure (quasi-hydrostatic) torsion at a true strain e = 4.7–5.8 is found to form two martensitic phases, namely, the ferromagnetic α phase with a high specific saturation magnetization and the paramagnetic ε phase. Two dispersed phases, which differ significantly in magnetic respect, largely explain the complex nature of changing the saturation magnetization with the strain and the high hardness of the alloy.

A study is performed of the effect intense laser heating has on the strength characteristics of the γ‑phase in iron–chromium–nickel alloys. We show that using laser radiation to heat the initial α-phase to the temperature of the α → γ transformation produces a γ-phase with much higher microhardness and yield stress than those of the equilibrium γ-phase. A possible mechanism of this phenomenon is discussed.

The metallophysical principles and technological aspects are considered for developing a new class of materials characterized by a spatial distribution of macroscopic zones with different physical and mechanical properties, as well as gradient materials. The potential for making such materials has been demonstrated by the example of alloys belonging to the iron-chromium-nickel system of the austenitic-martensitic class. The role of severe plastic deformation and heat treatment using laser radiation for the production of materials consisting of paramagnetic macroscopic zones distributed in a certain way within a ferromagnetic matrix is analyzed. The potential for using such materials for manufacturing active parts of electrical machine rotors are discussed.

The influence of severe plastic deformation by torsion in the Bridgman anvil on the lattice parameters of pure ferromagnetic metals Ni and Co is investigated by x-ray diffraction analysis. It is shown that torsion combined with strong compression leads to decrease in the lattice of these metals and to the change in the level of crystal lattice microstrains. The mechanisms of deformation influence on the lattice parameters are proposed.

The effects of high pressure torsion at 77 and 295 K on the phase composition of soft magnetic alloys (FeCo)100-xVx (x = 0 - 6.0) were studied by X-ray structure analysis, transmission electron microscopy and magnetometry. It was established that HPT leads to the suppression of excess γ-phase in alloys containing 3.0–6.0% V. It was concluded that the observed effect was a consequence of the martensitic transformation γ→α, due to deformation, along the lines of TRIP effect. It was established that suppression of the paramagnetic γ-phase leads to a noticeable increase in the specific magnetism of saturation.

This paper provides data about modern alloys with specific physical properties (precision alloys). The following aspects are provided and described: classification of these alloys, physical ways in which their properties are formed, and the main parts of their production technology. Several promising areas for creating new precision alloys with complex combinations of performance properties are considered.

The effect of high pressure torsion (HPT) at 77 and 295 K on the phase composition of (FeCo)(100)V--x(x )(x = 0-6.0) soft magnetic alloys were studied by X-ray diffraction, transmission electron microscopy and magnetometry. It was established that HPT leads to the suppression of excess gamma phase in the alloys containing 3.0-6.0% V. It was concluded that the observed effect by analogy with the TRIP effect is a consequence of the strain-induced gamma ->alpha martensitic transformation. It was found that the suppression of the paramagnetic gamma-phase leads to a noticeable increase in the specific saturation magnetization.

The effect of large plastic deformations at room temperature in a Bridgman anvil cell on the specific saturation magnetization of the DO3-type ordered (Fe–24 at % Al) alloy has been revealed. It has been found that torsion at high pressure and certain deformation parameters results in the complete suppression of long-range order in the alloy and in the corresponding increase in the specific saturation magnetization by 11% with respect to the equilibrium state. A theoretical model qualitatively describing the revealed phenomenon has been proposed.

The effect of severe plastic deformation in Bridgman anvils at room temperature on the specific saturation magnetization (SSM) of the ferromagnetic DO3 ordered Fe–24 at.% Al alloy was studied by X-Ray diffraction analysis and magnetic measurements. High pressure torsion at certain deformation parameters was shown to fully suppress the long-range ordering in the alloy and simultaneously increase its SSM by 11% relative to that in the equilibrium state. A theoretical model which qualitatively explains this phenomenon is proposed.

The influence of annealing at 520°C on the saturation magnetic field and coercive force of amorphous 2NSR Fe–Ni–B–Si alloys is investigated. As a result of annealing, the saturation magnetic field reaches 1000–1800 Oe. Regions of short-range order (clusters) with a direction in which the atomic pairs are ordered are thought to be formed in the alloys. The formation of the coercive force in amorphous 2NSR alloys is described.

The possibility of producing gradient materials, i.e. materials with pre-set distribution of areas having fundamentally different physical and mechanical characteristics, with the help of laser heat treatment was investigated. Using as an example austenitic-martensitic alloys of iron-chromium-nickel, subjected to cold plastic deformation led to formation of martensite, we show that using laser at the temperature higher than the temperature of reverse martensite transformation leads to the formation of areas of high-strength austenite having predetermined form inside the martensite matrix. Influence of austenite areas geometry on mechanical properties of gradient material was studied.