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.

We have studied the kinetics of the disorder → order (A1 → L10) transformation in Cu–56Au nonstoichiometric alloy at a temperature of 250°C. The disordered initial state of the alloy was produced by either quenching of samples from a high temperature or plastic deformation. The results demonstrate that the rate of atomic ordering in the quenched alloy is extremely low: the transformation needs approximately two months of annealing at a temperature of 250°C to reach completion. The rate of atomic ordering in predeformed samples is even lower. In both an as-quenched and an ordered state, the lattice parameters of the alloy under investigation slightly exceed those of the equiatomic alloy. Independent of the initial state of samples, their microhardness first rises in the course of atomic ordering and then falls off. The resistivity of Cu–56Au alloy in a well-ordered state has been shown for the first time to be ρ = 7.04 × 10–8 Ω m, which is far lower than was thought previously. The data we obtained have been used to assess the ratio of the phases present (order/disorder) in different stages of annealing.

The structure and electrical properties of the Cu-5.9 at.% Pd alloy were studied after its annealing for two months at 250 degrees C. As a result of such a long-term thermal treatment, in the XRD patterns taken from the alloy one can observe a weak superstructural (100) reflection, which seems abnormal, since the alloy can only be in the state of a disordered single-phase solid solution (as it follows from the generally accepted Cu-Pd phase diagram). Quantitative analysis of the X-ray diffraction patterns reveals the presence of two new phases with different contents of Pd. An assumption is made that L12 superstructure can be formed in the Pd-enriched phase. The specific features observed in the temperature dependence of electrical resistivity, as well as the TEM results, confirm this set-forth hypothesis of ours. Using the resistometric method, the temperature of the order-disorder phase transition in the alloy was estimated as Tc approximate to 340 degrees C. It is concluded that the position of the A1-(A1+ L12) phase boundary in the Cu-Pd phase diagram requires more precise definition in the region of compositions on the side of the low Pd content.

— We have studied the kinetics of the disorder → order ( A 1 → L 1 0 ) transformation in Cu–56Au nonstoichiometric alloy at a temperature of 250°C. The disordered initial state of the alloy was produced by either quenching of samples from a high temperature or plastic deformation. The results demonstrate that the rate of atomic ordering in the quenched alloy is extremely low: the transformation needs approximately two months of annealing at a temperature of 250°C to reach completion. The rate of atomic ordering in predeformed samples is even lower. In both an as-quenched and an ordered state, the lattice parameters of the alloy under investigation slightly exceed those of the equiatomic alloy. Independent of the initial state of samples, their microhardness first rises in the course of atomic ordering and then falls off. The resistivity of Cu–56Au alloy in a well-ordered state has been shown for the first time to be ρ = 7.04 × 10 –8 Ω m, which is far lower than was thought previously. The data we obtained have been used to assess the ratio of the phases present (order/disorder) in different stages of annealing.

Проведено исследование кинетики фазового превращения беспорядок → порядок ( A 1 → L 1 0 ) в нестехиометрическом сплаве Cu–56 ат. % Au при температуре 250°C. Исходное разупорядоченное состояние формировали либо закалкой образцов от высокой температуры, либо сильной пластической деформацией. Установлено, что скорость атомного упорядочения закаленного сплава чрезвычайно мала и превращение заканчивается приблизительно через 2 мес. отжига при температуре 250°C. Скорость атомного упорядочения предварительно деформированных образцов еще ниже. Обнаружено, что как в закаленном, так и в упорядоченном состояниях кристаллическая решетка исследуемого сплава немного больше по сравнению с эквиатомным сплавом. Установлено, что вне зависимости от исходного состояния образцов их микротвердость в процессе атомного упорядочения сначала возрастает, а затем снижается. Впервые показано, что удельное электросопротивление сплава Cu–56Au в хорошо упорядоченном состоянии составляет ρ = 7.04 × 10 –8 Ом м, что намного ниже, чем считалось ранее. На основе полученных данных построена зависимость соотношения фаз (порядок/беспорядок) на различных этапах отжига.

Electric properties and microhardness of the Cu–5.9 at % Pd alloy are studied. These characteristics are compared with those of pure copper and Cu–8 at % Pd alloy. The results obtained are discussed using literature data on the properties of compositions close to the stoichiometric Cu3Pd alloy. Dependences of the electrical resistivity of low-alloyed Cu–Pd alloys on the true strain and quenching temperature are plotted. An anomalous decrease in the electrical resistivity of the studied alloys was found to result from both plastic deformation and increase in the quenching temperature. Annealing in a temperature range of 200–300°С was found to lead to an anomalous increase in the microhardness and electrical resistivity. The anomalies found are explained from the viewpoint of the formation of short-range atomic order upon quenching of the low-alloyed Cu–Pd alloys.

A dilatometric study of wire samples of Cu-50at.%Au and Cu-56at.%Au alloys was carried out. A feature of this work is the measurement of the temperature coefficient of linear expansion in two directions simultaneously: longitudinal and transverse ones. It has been revealed that the atomic ordering by L10 type leads to a slight decrease in all the sizes of the initially quenched samples. However, the pre-deformed samples become longer at the ordering and simultaneously decrease in their cross-sections. It was concluded that the residual stresses in the deformed sample caused a predominant orientation of the tetragonal c-domains during the phase transition. The obtained results allowed drawing and comparing the temperature dependences of the change in the volume of alloys during heating. It is shown that the restructuring of the structure in both alloys occurs in similar temperature intervals, but with different kinetics.

A study was made of the changes in the linear dimensions of the ZlM-80 gold-copper alloy samples (with a content of 80 wt.% Gold) during atomic ordering. The initial disordered state in some samples of the alloy was formed by quenching from high temperature, other samples were disordered as a result of severe plastic deformation. It was found that the shape change of samples upon heating strongly depends on their initial state: ordering causes a decrease in the length of hardened wire samples, while the length of the initially deformed samples increases. It is shown that, regardless of the initial state, atomic ordering processes lead to a decrease in the volume of the alloy under study. The results obtained are of both scientific and practical interest.

The kinetics of the A1→B2 phase transition in the cryogenically deformed Cu-47at.%Pd alloy has been compared with that both after room-temperature deformation and after quenching from high temperature. For this aim, the evolution of the microstructure, electrical properties and microhardness of the alloy during disorder→order transformation at 400 °C were studied. It was shown that annealing at 400 °C for 1 h led to the formation of a uniform ultrafine-grained ordered structure in the cryo-deformed alloy. In turn, the annealing duration of 1 h is not enough to finish the ordering process in the quenched sample. It was found that some volume of the ordered B2-phase was formed in the cryo-deformed Cu-47at.% Pd alloy after holding at room temperature for 0.5 year.

The changes in the linear dimensions of ZlM-80 gold–copper alloy samples (with a gold content of 80 wt %) during atomic ordering are studied. The initial disordered state in some of the alloy samples is formed by quenching from a high temperature, and other samples are disordered as a result of severe plastic deformation. It is found that the change in the shape of specimens with heating strongly depends on their initial state: the ordering causes a decrease in the length of hardened wire specimens, while the length of initially deformed specimens increases. It is shown that the atomic ordering processes give rise, regardless of the initial state, to a decrease in the volume of the alloy under study. The obtained results are of both scientific and practical interest.

The microstructure, mechanical and electrical properties of Cu-Pd alloys (with Pd content not more than 8 at.%) and triple Cu-Pd-Ag alloys with 5 at.%Ag were studied. It was established that the strength and the recrystallization temperature of the Cu-Pd alloys increased with palladium content. A comparison of the electrical properties of these alloys when Pd content was increased from 0 to 8 at.%Pd was done. An anomaly was revealed in the Cu-5.9Pd and Cu-8Pd alloys: the plastic deformation does not lead to an increase in the electrical resistivity. It is due to the destruction of short range atomic order in the quenched Cu-Pd alloys under deformation. The alloying with silver leads to a further increase in strength with a constant electrical conductivity. It was found that annealing of the deformed Cu-Pd-Ag alloys at 200-300°C led to an increase in strength. It was shown that the effect was not related to the Pd-content and was due to silver only.

Cu/Mg-composites, the copper matrix of which contains 1, 7 and 2730 magnesium filaments, were obtained by hyrdoextrusion at room temperature. The structure, mechanical and electrical properties of the deformed composite rods and thin wires were investigated. The yield strength and electrical resistivity were theoretically calculated and these estimations were compared with the experimental results. The XRD-method allowed discovering a change of the lattice constant of the Cu-matrix under deformation of the composites. It has been concluded that, under severe plastic deformation, a supersaturated Cu-based solid solution forms on the Cu/Mg-interface. As a result, the strength of the deformed Cu/Mg-composite with minimal volume fraction but maximal surface area of magnesium is abnormally high. A thick Cu-sleeve provides low electrical resistivity of this Cu/Mg-composite. The obtained results can be used for the development of high-strength Cu-based conductors.

This paper presents the results of a study of the formation of the structure and properties of the 40Au–25.4Pd–34.6Cu alloy (wt %) in the course of its atomic ordering. A number of literature sources have been analyzed, and possible reasons for the deviation between experimental data of different authors are discussed here. Earlier field ionic microscopy (FIM) results have been confirmed: ordered В 2-phase nuclei in a matrix with an L 1 0 -superstructure were observed in this alloy after prolonged annealings. It has been shown that the kinetic of atomic ordering is abruptly accelerated in a field of external tensile stresses. The results of this work demonstrate the possibility to control the structure in the course of “disorder ↔ order” transitions and can be used for the creation of new approaches to the treatment of orderable alloys.

Two Cu/Mg-composite rods of different content of components were produced by hydrostatic extrusion. The volume proportion of the copper sheath and magnesium core was almost equal in one of the two composite samples. Seven thin magnesium fibers were located in the copper matrix of another composite. Estimate calculations of the strength properties and electrical resistance of deformed composites were carried out and compared with the experimental results. The influence of anneals on the microstructure and electrical and mechanical properties of composites was also studied. This work has shown that a temperature rise causes sequential formation of the intermetallic compounds CuMg2 and Cu2Mg at the Cu/Mg interface, which, according to the phase diagram, results in eutectic reactions. The results of this work can be used in the development of high-strength composite conductors.