The paper reveals the structure formation and magnetic properties of amorphous alloys based on the Fe-Co-Cr-B system with varying proportions of Fe to Co. These materials were obtained in the form of metal ribbons through the melt spinning technique in an inert atmosphere. In the initial as-spun state, the ribbons exhibited an amorphous structure characterized by their ferromagnetic properties. As the content of cobalt in the alloy composition decreased, the thermal stability of the amorphous phase matrix increased, leading to a shift in the crystallization mechanism from primary crystallization of the α solid solution phase to eutectic type crystallization of the initial amorphous phase. The phase composition of alloys during crystallization of the amorphous matrix phase is investigated. Alloys with a reduced cobalt content during the heating process undergo crystallization driven by the eutectic mechanism. This results in the formation of a mixture of α and Me3B phases. During this process, a significant increase in the magnetic moment of the alloys was detected. The α phase, which was formed by eutectic crystallization, was found to be enriched in chromium. It has been demonstrated that achieving a highly coercive state, it is contingent upon maintaining a Fe / Co ratio greater than 3, while simultaneously ensuring that the chromium content exceeds 16 at.%. The obtained data provides guidance for the development of functional materials with controlled magnetic properties.
This paper presents a modified small-angle X-ray scattering (SAXS) method for analyzing the size and shape of hardening particles in steels. Unlike the conventional SAXS approach, which typically analyzes alloy particles of only one morphology, the modified method enables simultaneous evaluation of various types of particles differing in both size and morphology. The essence of the modification to SAXS method is that it takes into account the contribution of the intensity of the separate types of particles with different morphologies to the total true intensity. For each type of particles, shape and structural coefficients are set taking into account their spatial distribution in the analyzed area. To detect the presence of particles of different morphologies in alloys, the experimental patterns are analyzed. First, based on the I(q−n) dependence, the morphology of the existing types of particles was traditionally identified (cylinder / needle (n =1), plate / disk (n = 2), and ellipsoid / sphere (n = 3, 4)). Subsequently, individual regions of the SAXS curve were analyzed in the context of optimizing the size and shape of various particles. The modified SAXS method was tested for analyzing the morphology and size of cementite particles in ferrite-pearlite steel subjected to annealing. As a result, it was shown that during the annealing process of steel, cementite particle morphology in pearlite grains undergoes a stepwise transformation according to the following scheme: lamellar → ellipsoidal → spherical. For the first time, quantitative characteristics of the change in particle size distribution were obtained for different morphologies. The transformation of cementite particle morphology was found to be accompanied by growth, which leads to a decrease in the contribution of dispersion hardening.
A method of wire electron beam additive manufacturing of cylindrical bimetallic products made of CuAl9Mn2 aluminum bronze and 13Mn6 ferrite-perlitic steel was proposed for the first time to achieve strong defect-free joining of components. Cylindrical bimetallic tribotechnical components based on 13Mn6 steel and CuAl9Mn2 bronze showed a high degree of structural homogeneity and defect-free gradient zone structure when bronze was applied over steel. When the steel component is applied over bronze, the degree of mutual mixing of the components in the gradient zone increases sharply due to the high temperature of the steel relative to the bronze base. This leads to the formation of defects in the form of cracks and delaminations in the boundary zone. Despite the inhomogeneous structure of the transition zone of the samples where steel is applied over bronze, no embrittlement of the material due to infiltration of bronze into the imperfections of the steel fragment is observed, and the mechanical properties of the steel and the transition zone even exceed the similar parameters of the samples where bronze is applied over steel. The studies have shown that by the method of wire electron beam additive technology it is possible to form large-size structures from heterogeneous materials with strong and defect-free connection of components. The results obtained show that there are still tasks for further modification of the technology of wire electron beam printing of products of “bronze−steel” system with application of steel over bronze.
Superplastic deformation of thin sheets is widely used in aerospace, automotive and other industries. In this paper, a mathematical model of plane strain superplastic pressure forming of a sheet specimen into a die is proposed. A die under consideration has a shape of a long box with an isosceles trapezoid cross section, but the model can be generalized for more complex die shapes. It is assumed that sticking happens between a shell and a die and thickness remains unchanged once contact occurs. The process of forming was divided into different phases, which are determined by the die geometry. For each phase, ordinary differential equations for thickness were derived along with the initial conditions. Solutions of obtained ODEs allow estimating the shell thickness at any point of a specimen as a function of coordinate along walls of the die and to determine the duration of each superplastic pressure forming phase for a given pressure-time function. Norton’s power law was used as a constitutive equation. Due to the simplicity of Norton`s law it is possible to solve some of ODEs analytically. The proposed model can be used with other types of constitutive relations, in particular with relations that include microstructure parameters etc. The superplastic forming of a Ti-6Al-4V titanium alloy sheet for the piecewise pressure-time function has been modelled. Some special cases of die geometry are analyzed.
Enhancing the strength, hardness, and wear resistance of aluminum alloys can be done through composite forming. According to the methods of production, composites can be classified into two types: ex situ and in situ composites. In ex situ composites, the reinforcing particles do not interact with the matrix, whereas in in situ composites, a chemical reaction occurs between the reinforcing particles and the matrix. Friction stir processing (FSP) is a promising approach to forming in situ composites, as it involves the frictional mixing of solid-state metal through the combined rotational and linear movement of the tool. The aim of this work was to study the impact of multi-pass FSP on the microstructure and microhardness of the in situ composite formed on the surface of an AA6063 alloy with pre-incorporated NiO particles. For this purpose, 4-, 10-, and 20‑pass FSP of AA6063 alloy sheets with grooves filled with fine NiO powder were performed. The chemical reaction between NiO and the aluminum matrix leading to the formation of Al3Ni and Al2O3 was studied using EDS, EBSD and X-ray diffraction techniques. It was found that the quantity of Al3Ni and Al2O3 particles increased with the number of FSP passes. The maximum surface microhardness of 253 HV is reached after 10 passes. As the number of FSP passes increases, the grain / subgrain sizes of the aluminum matrix decrease. After 10 passes, the grain / subgrain sizes stabilize at a level of 0.8 – 0.9 μm.