The ordered gold-copper alloy Cu–56 at

The ordered gold-copper alloy Cu-56 at % Au is widely used in instrument engineering as conductors of weak electrical signals in control devices. However, microstructural evolution and changes in the physicomechanical properties of the alloy during the disorder -> order phase transformation (A1 -> L1(0)) are still poorly understood. In the present paper, we study the evolution of the microstructure and properties of the quenched Cu-56 at % Au alloy during the disorder -> order phase transformation. The annealing time at 250 degrees C ranged from 10 min to 4 months. Microstructural studies were performed using transmission electron microscopy, the ratio of volume fractions of the ordered and disordered phases was determined using X-ray diffraction analysis and resistometric measurement, and material properties were measured in mechanical tensile and microhardness tests. The fraction of the ordered phase, strength properties, and specific electrical resistivity were plotted as a function of the annealing time. It is found that the maximum strength properties correspond to the two-phase state (A1 + L1(0)) of the alloy with an approximately equal phase ratio. It is shown that, with an increase in the fraction of the ordered phase, the tensile strain hardening coefficient almost doubles.

The intermetallic compound Al2Pt has potential of use in radiation sensing devices and selective solar absorbers, and is a promising protective coating of jet engine turbine blades. In our study, we demonstrate for the first time the possibility of forming nanocrystallites of the Al2Pt intermetallic compound in an Al-Pt disc produced by high pressure torsion (HPT) of elemental chips at cryogenic temperature. The composition of the Al + Pt mixture corresponds to the Al2Pt stoichiometry. Microhardness dependences against the distance from the disc center have been plotted and phase composition in the different points has been investigated. The formation of some high-strength phases was confirmed by a significant increase in microhardness near the edge of the cryodeformed Al-Pt disc. The Al2Pt intermetallic phase and amorphous phase were revealed both in XRD-scans and TEM-observations. The spread of Al2Pt crystallites sizes is wide and ranges from 10 to 200 nm. It was found that the amorphous phase had a composition of about 85Al-15Pt (at

The production of Al-based composites with high functional properties is an urgent scientific problem, the results of which may be of interest for practical application. That is why, there is an increasing interest in using the high pressure torsion (HPT) method to consolidate mixtures of aluminum with different metal powders and obtain new materials with promising properties. In the work, we obtained a novel metal-matrix composite, in which a soft Al-matrix is strengthened by hard and inert Pt-particles. The evolution of the phase composition and microhardness of the discs, which were produced by HPT of mixture Al+Pt chips, are investigated. Severe plastic deformation and large shear strain implemented under HPT lead to amorphization and solid solutions based on both Al and Pt. According to our estimation, near 5 at.% Al dissolved in Pt after the room-temperature HPT. Despite the fact that Pt is practically insoluble in Al, the XRD results of the Al-Pt disc suggest the formation of a non-equilibrium solid solution containing 2.1 at.% Pt in the Al matrix. The aluminum and platinum disks were also obtained and investigated. It was revealed, that the microhardness of the Al-Pt composite disc is between the microhardness values of Al- and Pt-discs.

The evolution of the microstructure, physical and mechanical properties of pre-deformed samples of the non-stoichiometric alloy Cu-56at.%Au in the process of the L1o-type atomic ordering was studied. The duration of annealing at 250 °C ranged from 1 hour to 2 months. Changes in microhardness and electrical resistivity at various stages of the disorder→order transition were found out, the microstructure was examined using a transmission electron microscope, XRD-scans and tensile tests were performed. Based on the resistometric results and XRD-analysis, the dependence of the fraction of the ordered phase vs. the annealing time was plotted. Consecutive changes in structural states observed during long-term annealing were considered through the competition between the energy of the elastic stresses, the surface energy and the energy of the dislocation structure. An abnormal increase in the strength properties of the alloy during annealing was found: the yield strength and microhardness of the initially deformed samples significantly increase (at 15% and 30%, respectively), at the same time there is a drop in electrical resistivity and an increase in plasticity. An attempt was made to describe the observed phenomena considering mutual effect of ordering and recrystallization. Discovered annealing hardening was explained in terms of the suppression of recrystallization by ordering, which is confirmed by the preservation of a high density of inherited dislocations in an ordered matrix and low plasticity of the annealed samples. The retardation in the recrystallization rate with an increase in the preliminary deformation strain of the alloy was discovered.

An innovative technology has been developed and implemented for the restoration and manufacturing of new mold copper plates for continuous casting machines (CCMs) using wear-resistant composite coatings. These copper plates significantly surpass the service life of imported copper plates featuring galvanic coatings, sometimes by up to 20 times. However, the pressing challenge of restoring the copper plates of molds once they have reached the minimum permissible thickness remains unresolved. This study aimed to explore the feasibility of restoring a plate composed of precipitation-hardening Cr–Zr bronze with the same material by employing friction stir lap welding (FSLW). The objectives were to examine the structure, quality, and hardness of the welded joint, alongside investigating the impact of heat treatment (quenching and aging). By utilizing multi-pass FSLW method with a rotating tool crafted from a heat-resistant alloy and overlapping (partially overlapping) successive passes, a welded joint with a thickness of ~5 mm was achieved, devoid of critical continuity flaws (cracks or voids). Within the bronze layer restored through FSW, a softening effect ranging from 85–105 HV1 was observed compared to the initial hardness of the bronze in its hardened and aged state while in service (116–126 HV1). This is attributed to recrystallization and overaging, specifically the coarsening of chromium particles within the Cr–Zr bronze due to the heating of the weld nugget (stir zone) to 600–700 °C. The observed softening effect during FSW can be effectively rectified through heat treatment involving dissolution of the hardening phases followed by aging, resulting in a hardness increase to approximately 120–150 HV1. The process of restoring copper plates to their original thickness via the progressive and environmentally friendly FSW method, followed be the subsequent application of wear-resistant composite coatings, presents the opportunity for an almost infinite operational cycle of molds. This advancement could potentially eradicate the necessity for Russia to rely on importing such molds copper plates.

A mixture of the Al 2 Au intermetallic compound and copper powders was compacted and then melted in an argon atmosphere to form an Al 2 Au + Cu ingot. Study of the structure of the alloy showed the formation of areas of the Al 2 Au intermetallic phase, which are brightly colored and are present in the AlAu intermetallic matrix. Thin Cu-enriched streaks occur inside the AlAu matrix. The optical characteristics of the prepared ternary compound have been measured. The microindentation of the intermetallic phases has been performed; the microhardness and contact elastic modulus have been determined.

The possibilities of surface strain hardening of austenitic stainless chromium-nickel steel AISI 321 (04Cr17Ni 8MnMoTi) using conventional ultrasonic impact treatment and a new method of ultrasonic impact-friction treatment with the tool tilt angles in the range of 90°–60° under conditions of limited lubricant supply were studied. Ultrasonic impactfriction treatment significantly improves the efficiency of surface hardening (up to 2.4 times) due to activation of shear deformation processes and, therefore, grain structure refinement. It is shown that a more acute angle between the tool axis and treated surface raises the amount of strain-induced α'-martensite in the surface layer, as well as leads to roughening of the surface microrelief.

Министерство науки и высшего образования Российской Федерации Российская академия наук Научный совет по неорганической химии РАН Научный совет по аналитической химии РАН Научный совет по химической технологии РАН Российское химическое общество имени Д.И

40 mm thick coarse-grained (up to 10 - 20 mm) CuCrZr mold wall to 2 mm thick pure copper plate lap joint was performed using friction stir welding (FSW) operating a H13 die steel tool. The obtained defect-free joint indicates the potential of FSW to restore worn-out copper molds wall. FSW resulted in ultrafine microstructure (0.5 -1.0 mu m) of stir zone strengthened by chromium and Cu5Zr nanoparticles. Grain boundary and dispersion hardening increase the hardness of the stir zone up to 150 -190 HV1 compared to 110 -130 HV1 of the initial coarse-grained structure. Based on the results, friction stir welding and related friction stir processing technologies are proposed as a severe plastic deformation method to obtain an ultrafine-grained state of CuCrZr alloys.

A mixture of fine powder of the Al2Au intermetallic compound and coarse Cu-powder was processed by the ball milling (BM) technique. The phase composition of the obtained powder product and the microstructure of separate particles were studied by TEM, SEM and XRD methods. It was found that BM for 4 h leads to the formation of Cu-clusters that are evenly distributed among the Al2Au-particles. There was discovered a decrease in the lattice parameter of the Al2Au-phase, which is associated with the formation of a solid solution of copper in Al2Au. The crystallite size in the resulting powder is near 20 nm. The mechanical properties of the (Al2Au + Cu)-powder were evaluated using nanoindentation tests. (c) 2021 Elsevier B.V. All rights reserved.

The study of the influence of phase transformations on residual stresses in heterophase materials is very important for predicting the service life of machines and constructions. Welded joints made of dissimilar materials are of particular interest. The chemical and phase compositions, microstructure, microhardness, strength, and fracture surface characterization of dissimilar AISI 321/Cu/Ti laser joints have been studied. Distinctive features of the laser welding conditions are the displacement of the focal spot to the steel/Cu interface and the deepening of the focus by 3 mm. The chosen mode of laser welding made it possible to obtain the following chemical composition of the melting zone (MZ): 55.3 wt% Cu, 32.2 wt% Fe, 8.5 wt% Cr, 4.0 wt% Ni, and 1.0 wt% Ti. After crystallization in MZ, two supersaturated solid solutions are formed: one based on copper and the other based on iron. During post-welding cooling, (Fe,Cr)(2)Ti intermetallic particles sized 10 nm homogeneously precipitate in the Cu-based solid solution, and 10-nm TiCu4 particles precipitate in the Fe-based solid solution. Fe-based regions become additionally hardened (to 540 HV 0.025) due to the formation of martensite crystals in the austenite matrix. Alloying of titanium with copper causes I3Ti stabilization at the interface Ti/MZ. During contact melting of titanium, Ti2Cu intermetallic particles of three types emerged: from 2 to 5 mu m eutectic, from 0.1 to 0.5 mu m eutectoid, and those homogeneously precipitated in beta Ti during cooling, sized 10 nm. After quickly cooling, the compressive residual stresses formed in the welded joint. When specimens with welded joints were tensile tested, they fractured in the MZ according to a mixed type. Ductile fracture occurred in Cu- and Fe-based microconstituents by the MZ zone; brittle fracture occurred in the zone with (beta Ti + Ti2Cu) structure near Ti. The ultimate tensile strength of the resulting welded joints is 470-515 MPa, and this significantly exceeds the available data.

The effect of the frictional treatment with a sliding indenter on the micromechanical properties of the austenitic corrosion-resistant chromium–nickel AISI 321 steel (16.80 wt % Cr, 8.44 wt % Ni) has been investigated. The instrumented microindentation results, which was performed on the surface of the steel and at different depths from the surface, has shown the exponential distribution of maximum hmax and permanent hp indentation depths, Martens hardness HM, indentation hardness at the maximum load HIT, elastic reverse deformation work of indentation We, total mechanical work of indentation Wt, elastic recovery Rе, ratio of indentation hardness to contact elastic modulus НIT/Е*, power ratio $${{H_{{{\text{IT}}}}^{3}} \mathord{\left/ {\vphantom {{H_{{{\text{IT}}}}^{3}} {{{E}^{{*2}}}}}} \right. \kern-0em} {{{E}^{{*2}}}}}$$ , and plasticity index δA over the depth of the hardened gradient layer. In this case, the HM, HIT, We, Rе, НIT/Е*, and $${{H_{{{\text{IT}}}}^{3}} \mathord{\left/ {\vphantom {{H_{{{\text{IT}}}}^{3}} {{{E}^{{*2}}}}}} \right. \kern-0em} {{{E}^{{*2}}}}}$$ values are the highest, whereas the hmax, hp, Wt, and δA values are the lowest for the steel surface. The E* contact elastic modulus of AISI 321 steel also increases after the frictional treatment. It is distributed nonmonotonously over the depth of the hardened layer. This can be explained by the formation of different dislocation structures on the steel surface and in the underlying layers. The indentation results have shown that the frictional treatment increases the resistance to mechanical action of both the steel surface and the hardened layer with a depth of to 500 µm.

In the alloy Fe 63.5 Ni 10 Cu 1 Nb 3 Si 13.5 B 9 , which is conventional FINEMET with Fe replaced by 10 at % Ni, the effects of the temperature and time of nanocrystallizing annealing in the presence of tensile stresses (stress annealing, SA) on the magnetic properties, magnetic anisotropy, and structure are considered. In the entire studied SA temperature range (480–550°С), induced magnetic anisotropy (IMA) of the easy-plane type occurs in the studied alloy. The tensile stresses upon SA were 200 MPa. In the course of SA at the minimum temperature, anisotropy with the minimum IMA constant (200 J/m 3 ) is induced. The maximum SA duration, i.e., 4 h, is required. At SA temperatures of 540–550°С, 10 min is sufficient to induce IMA with the maximum constant ~2000 J/m 3 . It is shown that the structural state (phase composition) is correlated with the magnetic properties and IMA. Thus, the increase in the coercivity with an increase in the SA duration at 540–550°С (as well as at 520°С) is due to the development of the tetragonal phase in the alloy. The α‑(Fe,Ni)Si solid solution and Fe 3 Si phases form upon treatment for 10 min. The decrease in the IMA constant with an increase in the SA time at 540–550°С from 10 min to 1 h is most likely due to the change in the volume fractions of the structural components of the alloy with negative and positive magnetostriction.

CrAlSiC films deposited under various conditions of carbon-plasma generation (PVD or PACVD) are investigated. A plasma source of cathodic-arc discharge with a Cr–Al–Si cathode and a source of pulsed cathodic-arc discharge with a graphite cathode are used for the deposition of a CrAlSiC(I) film. A plasma source of cathodic-arc discharge with a Cr–Al–Si cathode and a gas-discharge device for generating a non-self-sustaining discharge in an argon-acetylene mixture are applied for the deposition of a CrAlSiC(II) film. The sources work together in both processes. The film structure is investigated using electron microscopy and Raman spectroscopy. The hardness and elasticity modulus are determined by nanoindentation; the friction coefficient is tested with the reciprocating motion of a steel ball without lubrication. It is found that the condition of generating carbon plasma (graphite sputtering or destruction of acetylene) has a significant effect on the structure and properties of CrAlSiC. CrAlSiC(I) consists of an amorphous phase with inclusions of silicon-carbide nanograins 10–30 nm in size. On the surface there are protrusions with a size of 2–4 µm. These features provide a high hardness and low friction coefficient. No crystalline formations are found in the amorphous matrix of CrAlSiC(II). On the surface there are bubble-like formations up to 15 microns in size. This coating is inferior to CrAlSiC(I) in terms of hardness and resistance to friction. Under friction the film is destroyed by chipping fragments. CrAlSiC(I) can be recommended for practical application.

The structure and micromechanical properties of a 316L stainless steel produced by the selective laser melting (SLM) technique have been studied in its initial state and the following heat treatment: quenching from 1050 °C and 4-hour annealing at 480 °C. The heat treatment does not result in changing the steel phase composition, however, it reduces the microhardness by 5%, HM hardness (Martens hardness) by 12% and indentation hardness by 16% at Hit maximum load. The heat treatment also increases the E* contact elasticity modulus by 14% due to the lower porosity of the material. As soon as heat treatment provides no strengthening of the steel synthesized by SLM, deformation processing, chemicothermal treatment and application of thin coatings may become quite promising strengthening methods.

The increased anticorrosive, strength, tribological, and physical characteristics are the specific features of steels with high nitrogen content. Searching for the ways to strengthen high-nitrogen steels is a promising area of contemporary metal science. Heat treatment is one of the methods of hardening nitrogen steels as a result of precipitation hardening with nitride particles. The authors studied the influence of short-term high-temperature aging and large plastic deformations implemented by shear under the pressure of 8 GPa (SP method) on Bridgman anvils (three revolutions of anvils with the rotation velocity of 0.3 rev/min) at room temperature on the structural-phase transformations and micromechanical properties of the 08H22GA1.24 high-nitrogen steel with the mixed γ (austenite) +  (ferrite) metal matrix structure. The study identified that aging (0.5 h) at the temperature of 650 °С of steel quenched at the temperature from 1180 °С causes the formation of the mixed austenitic-ferritic structure of metal matrix in the ratio of 50 vol. % of  and 50 vol. % of α and the release of extended secondary Cr2N chromium nitrides, together with ferrite interlayers forming the areas with the pearlite-like structure. These areas cause the increased microhardness of steel with the austenitic-ferritic matrix structure (385±8 HV 0.025) compared to one of steel aged at the temperature of 550 °С (0.5 h) and having an austenitic matrix structure strengthened with secondary CrN nitrides (364±8 HV 0.025). The SP deformation of steel aged at the temperature of 650 °С (0.5 h) with the initial ++Cr2N structure leads to →ʹ transformation and the formation of submicro- and nanocrystalline structures. It causes the effective strength improvement of steel (up to 900±29 HV 0.025) and the growth of resistance to elastoplastic deformation compared to aged at the temperature of 550 °C (0.5 h) condition.

Results are provided for studying deformation methods of steel surface nanostructuring and hardening with martensitic, pearlitic and austenitic structures. A new method of ultrasonic impact-friction treatment is considered. Combined methods of nanostructuring treatment (friction treatment + annealing) are proposed for a metastable Cr – Ni steel. The possibility is demonstrated of activating steel saturation with nitrogen during plasma treatment due to preliminary nanostructuring friction treatment.