Maxim Yurievich Murashkin

Two alloys with similar chemical composition—Al–0.5 wt % Fe were produced via two different production technology being casting into electromagnetic mold (EMC) and continuous casting and rolling (CCR), respectively. Production methods provided different cooling rates resulting in different structure formation and sets of properties, such as mechanical strength, elongation to failure and electrical conductivity. Samples of the alloys were subjected to the combination of the equal-channel angular pressing by the “Conform” scheme and cold drawing (ECAP-С + CD), as well as cold drawing (CD) only. It was demonstrated that the difference in production process provided distinct structural states, mainly different in size and distribution of the intermetallic particles. Differences in the morphology of the intermetallic particles notably affected the physical and mechanical properties of the alloys, mainly electrical conductivity. Thermal stability of the alloys, measured according to the international standard for thermal-resistant aluminium alloy wire for overhead line conductor, differs as well, depending on the particle morphology—EMC alloy retains 94–98% of its ultimate tensile strength after annealing, while CCR alloy only 60–83%.

This work is dedicated to the analysis of the influence of the core material on the complex of physical and mechanical properties of copper-clad aluminum wires (CCAW) in hard (hard-drawn) and soft (annealed) states. Low-alloyed aluminium alloys of the Al–Fe system were chosen as research material as an alternative to the conventionally used technically pure aluminium in terms of thermal stability, mechanical strength and ductility. Such alloys, while still retaining low cost and high electrical conductivity, are characterized by the improved relative to technically pure Al mechanical strength and thermal stability. Alloys used in this study were produced by casting into electromagnetic mold to further improve their mechanical properties. Three different alloy compositions Al–0.5 wt % Fe, Al–0.5 wt % Fe–0.3 wt % Cu and Al–1.7 wt % Fe were used. To achieve a hard-drawn state, the copper-clad wire was cold-drawn to a reduction degree of 90%, and the soft state was achieved by annealing at 300 and 325°C for 1 h. To compare CCAW with the core materials produced by electromagnetic casting, samples with similar copper content were produced based on commercial alloy 8176, produced by a traditional combined casting and rolling method. Based on the experimental data obtained and the results of the optimization performed (from the combined tensile strength, ductility and electrical conductivity point of view) using the linear convolution target function, the most suitable alloy of the Al–Fe system as the core material for the CCAW was proposed.

The research status on such functional properties, as bending capability, wrapping capability and ductility of conductive Al–Fe and Al–Fe–Cu alloys wires is uncertain. Bending and wrapping capability is determined by the industrial standards while no attempts were made to study the relation between them and ductility of the Al alloys wires, paying even less attention to the ultrafine-grained Al-based wires, produced by electromagnetic casting and equal-channel angular pressing. In this study alloys with two different chemical compositions (Al–0.5 wt. % Fe and Al–0.5 wt. % Fe–0.3 wt. % Cu) and two different casting methods (casting into electromagnetic mold and continuous casting and rolling) were used. Part of the wires for the study was prepared by cold drawing (CD), the other part – by the combination of the equal-channel angular pressing by the Conform scheme and cold drawing (ECAP-C+CD) to obtain coarse grained (CG) and ultrafine grained (UFG) structures, respectively. Annealing at 230 °C for 1 h was carried out to evaluate the thermal stability of the wires. It was shown that the correlation between ductility (elongation to failure), number of wraps and number of bends (both before the first crack and before complete failure of the specimen) may differ depending on the deformation value, deformation scheme, and amount of alloying elements of the alloy wire, as well as ability to form solid solutions.

The modern electrical engineering industry requires cheap and easily reproducible aluminum alloys with advanced mechanical strength and electrical conductivity. This work studies the influence of small (up to 0.3 wt. %) copper additions on the microstructure and physical and mechanical properties, as well as phase transformations in the Al–Fe system alloys with an iron content of 0.5 and 1.7 wt. %, produced by continuous casting into electromagnetic crystallizer. Alloys of the above chemical compositions were produced, and subsequently annealed at 450 °C for 2 h. In all states, the microstructure (via SEM), yield strength, ultimate tensile strength, elongation to failure, and electrical conductivity were studied. It has been shown that copper additions lead to an increase in the strength of both alloys and a slight decrease in their ductility compared to similar materials without copper. An increase in strength and a decrease in ductility due to the copper addition is associated with the formation of more dispersed intermetallic particles in copper-containing Al–Fe system alloys. Additional spheroidizing annealing leads to a decrease in the length of the interphase boundary between the aluminum matrix and iron aluminide particles due to a change in their morphology, which leads to an increase in electrical conductivity. In general, copper-containing alloys showed higher mechanical strength with lower electrical conductivity, as well as higher thermal stability.

The addition of the 0.3 wt. % copper to the Al-0.5 wt.% Fe alloys was studied. The initial billets of the alloy were produced via electromagnetic casting ( The addition of the 0.3 wt. % copper to the Al-0.5 wt.% Fe alloys was studied. The initial billets of the alloy were produced via electromagnetic casting (

The influence of additional deformation heat treatments (DHTs), implemented by two regimes: (1) annealing and small additional deformation by high-pressure torsion (HPT) at room temperature (RT) and (2) HPT at elevated temperature to 10 turns and small additional HPT at RT, has been studied on the microstructure, mechanical properties and electrical conductivity of ultrafine-grained (UFG) Al-0.53Mg-0.27Zr (wt.%) alloy structured by HPT to 10 turns at RT. As is shown, both types of additional DHT lead to a substantial increase in plasticity (2–5 times) while maintaining high electrical conductivity (~53% IACS) and strength comprising 75–85% of the value in the pre-DHT state of the UFG alloy. The possible physical reasons for the revealed changes in the physical and mechanical properties are analyzed. Comparison of the strength and plasticity changes with the microstructure evolution after DHT of both types indicates that the increase in the density of introduced grain boundary dislocations is the most probable factor providing a tremendous increase in plasticity while maintaining a high level of strength in the UFG alloy under study. An outstanding combination of high strength (370 MPa), high elongation to failure (~15%) and significant electrical conductivity (~53% IACS) was achieved for the Al-Mg-Zr alloy. This combination of properties exceeds those obtained to date for this system, as well as for a number of other commercial conductor alloys based on the Al-Zr system.

This paper features the changes in microstructure and properties of an Al–Fe alloy produced by casting with different solidification rates followed by severe plastic deformation and rolling. Particularly, different states of the as-cast Al–1.7 wt.% Fe alloy, obtained by conventional casting into a graphite mold (CC) and continuous casting into an electromagnetic mold (EMC), as well as after equal-channel angular pressing and subsequent cold rolling, were studied. Due to crystallization during casting into a graphite mold, particles of the Al₆Fe phase are predominantly formed in the cast alloy, while casting into an electromagnetic mold leads to the formation of a mixture of particles, predominantly of the Al₂Fe phase. The implementation of the two-stage processing by equal-channel angular pressing and cold rolling through the subsequent development of the ultrafine-grained structures ensured the achievement of the tensile strength and electrical conductivity of 257 MPa and 53.3% IACS in the CC alloy and 298 MPa and 51.3% IACS in the EMC alloy, respectively. Additional cold rolling led to a further reduction in grain size and refinement of particles in the second phase, making it possible to maintain a high level of strength after annealing at 230 °C for 1 h. The combination of high mechanical strength, electrical conductivity, and thermal stability can make these Al–Fe alloys a promising conductor material in addition to the commercial Al–Mg–Si and Al–Zr systems, depending on the evaluation of engineering cost and efficiency in industrial production.

This study aims to achieve an ultrafine-grained (UFG) Al 2024 alloy superplasticity at temperatures lower than the traditional ones for commercial Al alloys (400–500 °C). The UFG structure with a mean grain size of 100 nm produced in the alloy by high-pressure torsion at room temperature provided a very high strength—microhardness (HV_0.1) of 286 ± 4, offset yield strength (σ_0.2) of 828 ± 9 MPa, and ultimate tensile strength (σ_UTS) of 871 ± 6 MPa at elongation to failure (δ) of 7 ± 0.2%. Complex tensile tests were performed at temperatures from 190 to 270 °C and strain rates from 10⁻² to 5 × 10⁻⁵ s⁻¹, and the values of flow stress, total elongation and strain rate-sensitivity coefficient were determined. The UFG alloy was shown to exhibit superplastic behavior at test temperatures of 240 and 270 °C. For the first time, 400% elongation was achieved in the alloy at an unusually low temperature of 270 °C (0.56 T_m) and strain rate of 10⁻³ s⁻¹. The UFG 2024 alloy after superplastic deformation was found to have higher strength (150–160 HV) than that after the standard strengthening heat treatment T6.

The influence of decreased temperature of tensile testing on annealing-induced hardening (AIH) and deformation-induced softening (DIS) effects has been studied in an ultrafine-grained (UFG) Al–Zr alloy produced by high-pressure torsion. We show that the UFG Al–Zr alloy demonstrates a DIS effect accompanied by a substantial increase in the elongation to failure δ (up to δ ≈ 30%) depending on the value of additional straining. Both the AIH and DIS effects weaken with a decrease in the tensile test temperature. The critical deformation temperatures were revealed at which the AIH and DIS effects are suppressed. The activation energy Q of plastic flow has been estimated for the UFG Al–Zr alloy in the as-processed, subsequently annealed and additionally strained states. It was shown that the annealing decreases the Q-value from ~80 kJ/mol to 23–28 kJ/mol, while the subsequent additional straining restores the initial Q-value. Alloying with Zr results in the expansion of the temperature range of the AIH effect manifestation to lower temperatures and results in the change in the Q-value in all of the studied states compared to the HPT-processed Al. The obtained Q-values and underlying flow mechanisms are discussed in correlation with specific microstructural features and in comparison to the UFG Al.