Scanning and transmission electron microscopies are used to study the microstructure and phase composition of the surface layer of Zr–1

The evolution of the structure and properties of an Al–1.8

Рассмотрены динамические свойства объемно-структурированных образцов с разной топологией сетчатых структур из алюминиевого сплава АК6, синтезированных селективным лазерным сплавлением. Испытания проведены при квазистатических скоростях деформации 102 ÷ 103 с‒1 методом Кольского с использованием разрезного стержня Гопкинсона. Построены диаграммы деформирования, и определены значения условного предела текучести и предела прочности. Проведено сравнение результатов измерения свойств образцов с разной топологией сетчатых структур — кубические типа ГЦК и ОЦК и трижды периодических поверхностей минимальной энергии типа гироид. Исследовано влияние геометрических характеристик гироидов (размер ячейки, толщина стенки) на прочностные свойства образцов. Показано, что при одной и той же плотности материала гироиды обладают повышенными характеристиками. Сетчатые металлические материалы, полученные аддитивной технологией, могут быть использованы в технике для уменьшения массы конструкций и ослабления разрушающих высокоэнергетических механических воздействий. Dynamic properties of volume-structured samples with different topology of mesh structures made of AK6 aluminum and synthesized by selective laser melting are considered. Tests are carried out at quasistatic strain rates of 102 ÷ 103 с‒1 by the Kolsky method using a split Hopkinson bar. Strain diagrams are constructed, and the values of the conditional yield strength and tensile strength are determined. The results of measuring the properties of samples with different topology of mesh structures of FCC and BCC types and triply periodic surfaces of minimum energy of the gyroid type. The effect of the geometric characteristics of gyroids (cell size and wall thickness) on the strength properties of the samples is described. It is shown that gyroids have improved characteristics at the same material density. Mesh metal materials obtained by additive technology can be used in engineering to reduce structural mass and destructive high-energy mechanical effects.

The effect of nanosecond pulse laser processing of the Zr–1

Scanning and transmission electron microscopies are used to study the microstructure and phase composition of the surface layer of Zr-1% Nb alloy, which was subjected to treatment by nanosecond laser pulses. During laser treatment, a thin strengthened surface layer with the fine microstructure is found to form. The strengthening of the surface layer no less than 4 mu m thick is proved to be due to the formed twin micropackets consisting of martensite nanolamellas and nano-sized omega-Zr phase.

Heat treatment of materials, including-in particular-two-stage T6I6 treatment, enables the nucleation of precipitates with a two-phase structure: core and shell. The above-mentioned treatment can be used to harden materials by selecting suitable treatment parameters and the chemical composition of the material that initiates a selective diffusion of the alloying elements. In this paper, tests of the T6I6 treatment were carried out on the EN AW-2024 alloy. The aluminium alloy was subjected to T6I6 treatment, and then the element distribution map was examined within the precipitate using the EDS method. The mechanical properties of the precipitate were tested using the nanoindentation method, and the kinetics of the formation of the precipitate were analysed using DSC. The impact of two-phase precipitates on the mechanical properties was determined through a static strength test, whereas the impact of the structure on the above-mentioned mechanical properties was determined based on HR-TEM observations. The results of the study confirmed the formation of a precipitate with a two-phase structure (shell; core) in the EN AW-2024 alloy, as well as the kinetics of their formation as a function of the parameters of the T6I6 process, such as temperature, duration and cooling rate. Strength tests confirmed an increase in the strength of the alloy to Rm = 520 MPa, with elongation remaining the same at A = 13.2%. HR-TEM observations, in turn, proved that the shell forming on the core is coherent with solid solution alpha, which means that the hardening of the alloy may occur as a sum of the Mott-Nabarro, Friedel and Ashby-Orowan mechanisms.

An investigation is performed of the effect produced by the technological parameters of a complex procedure for obtaining 3D printing powder of a new Nikalin aluminum alloy during dispersion in a ball mill, with the subsequent spheroidization of particles while processing the plasma.

Monolith and bulk-structured samples of different densities have been obtained using selective laser melting on a Realizer SLM 100 3D-printer intended for metals. Their quality and structure have been estimated via metallography and scanning electron microscopy. The correlation has been established between the parameters of synthesis, namely, between the intertrack distance and layer thickness at a laser power of 200 W, on the one hand, and structural characteristics, on the other. Based on the experimental results, the optimum operating parameters of a 3D-printer were found to obtain the Al–Cu–Mg–Si samples with dispersed structure and high mechanical properties. The features of the synthesis of bulk-structured samples with cubic geometry of plotting have been studied, and the types of defects that affect the quality and mechanical properties of samples have been determined.

The phase composition and structure of as-cast and deformed Al-1.53Cu-1.66Mn-0.38Zr-0.15Cr-0.15Fe (wt.%) were investigated. The radial shear rolling was used for the deformation of the alloy. The structure of as-cast alloy consists of aluminum solid solution, eutectic Al-6(FeMn) and Al2Cu, as well as Al7Cr and Al20Cu2Mn3 dispersive particles. It is assumed that radial shear rolling results in the refinement and partial dissolution of Al20Cu2Mn3 dispersoids. Along with this, significant grain refinement was established after deformation. The average grain-subgrain size in the alloy after deformation is 1.6 mu m. After deformation the alloy has the yield stress of 83 MPa and ultimate strength of 216 MPa. The elongation to failure of the deformed alloy is 25 %. Owing to the partial deformation induced dissolution of the aluminides and supersaturated solid solution formation, there is a potential for strengthening upon heat treatment of the alloy and improvement of its thermal resistance.

Composites based on Al-Fe alloys and reinforced with three-layer graphene sheets were synthesized "in situ" under a layer of molten salts. Composites containing 0.12 wt.% graphene were subjected to severe plastic deformation via high-pressure torsion. SEM and TEM were used to study the morphological and size characteristics of the composite structure in the as-cast and deformed states. Herein, it is shown that severe plastic deformation leads to the deformation-induced dissolution of iron-containing aluminides with the formation of a supersaturated Al solid solution with a submicrocrystalline structure. The hardness and electrical properties of the graphene composites were measured in different structural states and compared to the characteristics of the matrix alloy.

Composites based on Al-Mg alloy, reinforced with graphene nanofilms, were obtained by in situ synthesis under a layer of salt melt. Using SEM and HRTEM, the morphological and dimensional characteristics of the structural components of composites with different contents of graphene were studied. An experiment on dynamic compression of composites by the Kolsky method was carried out, dynamic properties were measured, and the evolution of a cast structure during high-speed deformation was considered. For the first time, the dynamic properties of composites under loading by plane shock waves have been determined. The dynamic properties of aluminum matrix composites are compared depending on the properties of the non-reinforced alloy.

The effect of high pressure torsion (HPT) on the structure and microhardness of Al3Ca2La1.5Mn alloy containing 13 vol% of Al-4(Ca,La) eutectic phase has been studied using electron microscopy, X-ray analysis and atom probe tomography (APT). We show that HPT causes the formation of a nanocrystalline structure resulting in a 4-fold increase in the microhardness (to 2.5 GPa) of the alloy. Post-deformation low-temperature annealing further increases the microhardness to similar to 3.1 GPa. The APT data suggest that the increase in the microhardness after annealing is caused by precipitation hardening due to the decomposition of the calcium and manganese supersaturated aluminum solid solution.

The method of high-resolution scanning and transmission electron microscopy was used to investigate the features of the formation of the structure and deformation behavior of a composite material based on aluminum with microadditions of graphene under severe plastic deformation by the dynamic channel-angular pressing method. It was found that an aluminum-graphene composite with a submicrocrystalline structure with the hardness 2.5 times higher than in the as-cast state forms in the deformation process. For the first time, the dynamic properties of the composite were measured under loading by plane shock waves at a speed of 5.0.10(5) s(-1). Comparison with the dynamic characteristics of a coarse-crystalline composite showed an increase in the dynamic elastic limit and dynamic yield stress by 1.8-2.0 times. (C) 2020 Elsevier B.V. All rights reserved.

In the paper, the structure and static and dynamic mechanical properties of ultrafine-grained A5083 alloy (Al-Mg-Mn) produced by high-pressure torsion (HPT) are reported. The static yield stress and tensile strength were determined in tensile tests at a strain rate of ~ 10−3 s−1, and the dynamic yield stress and spall strength were calculated from free-surface velocity histories obtained during shock-wave loading at a strain rate of 105 s−1. The HPT technique provides strong grain refinement. The average grain size of the alloy after HPT is 100-180 nm and depends on the accumulated true strain. HPT significantly improves the static strength properties of the alloy. The static yield stress is increased by 360-390% and the static ultimate tensile strength by 166-182%. It is shown that the dynamic yield stress improved by 168-181%, while the dynamic spall strength was not improved by HPT. Moreover, the nanostructured alloy with a grain size of ~ 100 nm demonstrates the lowest spall strength.

The features of structure formation in a nickalin eutectic aluminum alloy were investigated under high-pressure torsion. It is shown that this method makes it possible to create a submicrocrystalline composite consisting of an Al matrix and dispersed Al9FeNi eutectic aluminides. The influence of preliminary thermal treatment on the phase composition and structure of the deformed composite is considered. The mechanical properties of the nickalin were measured in a wide range of loading conditions, from static to dynamic.

A number of regularities of phase and structural transitions in an economically iron and nickel doped aluminum alloy with eutectic-forming elements (nikalin) at high shear strains under pressure have been determined in this work. The structural evolution of nikalin, in particular, the change in the morphology and sizes of its structural components, such as solid Al solution grains and eutectic aluminides Al 9 FeNi, was studied by scanning and transmission electron microscopy. The torsion of nikalin under high pressure was determined to result in the formation of a strengthened composite material with a submicrocrystalline Al matrix and dispersed (1.5–2.0-µm) particles of transition–metal aluminides. Kolsky dynamic compression and plane shock wave loading experiments were performed, and the mechanical behavior of nikalin with different structures was studied within a strain rate range of 10 –4 –10 5 s –1 . The dynamic characteristics of nikalin were compared with the mechanical properties determined in static tests.

An Al–Si eutectic alloy was synthesized by the selective laser melting (SLM) method using a pilot wrought Al-Si powder (of Russian AKD-12 grade) as the starting material. On the basis of electron microscopy, the microstructure of the SLM alloy was certified with EDS mapping of elements (Al and Si). It has been established that the main structural component is an Al-based solid solution with a cellular-dendritic structure (with an average cell size of ~500 nm). The Si phase, which is a component of the eutectic, is located at the boundaries in the form of rounded crystals about ten nanometers in size. This paper presents the results of measuring the mechanical and nanomechanical properties, which show the competitiveness of the use of the pilot (experimental) powder.

Abstract—In this work, the resistance of high-strain rate deformation and fracture during shock-wave compression of aluminum alloy A5083 previously obtained in two structural states by torsion under high pressure or dynamic pressing is studied. It is shown by electron microscopy that sub-microcrystalline structures differ in the size of grain–subgrains, dislocation density, and ratio of low-angle and high-angle boundaries. It is established that, at the same grain size, the sub-microcrystalline alloy exhibits higher dynamic properties, and after dynamic pressing, it has higher spall strength.

This paper describes the structural studies of hollow cylindrical shells made of D16 and Al-Mn aluminum alloys, loaded by sliding detonation. Explosive loading conditions for the complete convergence and closure of shells are established. Light optics scanning electron microscopy, and transmission electron microscopy are applied to study the structural and phase transformations in shells under shock wave loading. The relation of composition, structure, and mechanical characteristics of alloys with their behavior under the action of shock loading is shown. There are several scenarios of convergence of shells, depending on their composition and loading conditions-from complete and steady convergence to multiple spalling.