Russian Journal of Non-Ferrous Metals最新文献

In this study, an Al7075 matrix composite reinforced with nano-sized fly ash (FA) and cenosphere (CS), a waste product from thermal power plants, was fabricated using an ultrasonic cavitation-assisted stir casting method. These nanoparticles were added at amounts of 0.6, 1.2, and 1.8 weight percent. Microstructural inspection using scanning electron microscopy (SEM) was conducted to verify the dispersion of particles in the composite. The tensile strength, compressive strength, and hardness of the composite were determined through mechanical characterization. Results depict that, for the Al7075/FA_1.8 composite, the ultimate tensile strength, ultimate compressive strength, and hardness values have improved by 47, 26, and 30%, respectively, compared to the AL7075 alloy. For Al7075/CS_1.8, the composite ultimate tensile strength, ultimate compressive strength, and hardness value have been improved by 59, 34, and 37%, respectively, compared to the Al7075 alloy. A sliding wear test assesses the wear characteristics of the composite. In comparison to the Al7075 alloy, a maximum improvement of 63% in wear rate has been reported for the Al7075/FA_1.8 composite. Moreover, a maximum improvement of 72% has been observed for the Al7075/CS_1.8 composites compared to the Al7075 alloy.

The one-way and two-way shape memory effects as well as the superelasticity and the strain variation on cooling and heating under stress were studied in the cast Ti_40.7Hf_9.5Ni_49.8 – xCu_x (x = 1, 5, 10 at %) alloys. It was found that after preliminary deformation by tension in martensite state, the maximum value of shape memory effect was close to 4% for the alloys with x = 1 and 5 at % and 5.3% for the alloy with x = 10 at %. The maximum value of the two-way shape memory effect was equal to 2% and hardly depended on the Cu concentration in the alloys. This value was several times higher than the values previously observed in the quaternary Ti–Hf–Ni–Cu alloys. The maximum value of the recoverable strain observed on cooling and heating under constant stress did not depend on the copper concentration in the alloy and it was close to 6%. In the alloys with x = 1 and 5 at %, the recovery coefficient after cooling under stress was higher than after active deformation in the martensite state. In the alloy with x = 10 at %, the recovery coefficient was not affected by the way of the preliminary deformation. It was found that an increase in the copper concentration increased the volume fraction of martensite transforming into austenite on unloading, however the strain recovery was not complete on unloading. This was due to the manifestation of the martensite stabilization effect and that the critical stress for martensite nucleation was close to the yield limit for dislocation slip in the studied alloys.

Multicomponent brass alloys are widely used in various industries owing to their exceptional mechanical properties, wear resistance, and corrosion resistance. However, the well-known issue of low crack resistance in binary brasses and their instability during processing limits of their application. The hot deformation temperature of brasses coincides with the dissolution temperature of silicides in the alloy, leading to the formation of unstable regions, loss of coherence between silicides and the matrix, and subsequent spalling under operational loads. Diffusion processes associated with the formation of such structures hinder the further development of phase transformation of the α phase into Widmanstätten or bainitic structures. This work explores the possibility of enhancing the wear resistance and processability of brasses by introducing phosphorus, which promotes stabilization of the α phase and the formation of larger intermetallic compounds. At phosphorus concentrations in the range of 0.15–0.50%, silicon is displaced, resulting in the formation of metastable formations. The results of research provide a foundation for developing new alloys with improved performance characteristics.

Nowadays, the use of laminated composites is in huge demand in several industries due to the specific characteristics of the prepared material. Friction stir additive manufacturing (FSAM) method involves layer by layer addition where reinforcement particles can be embedded between the two layers to prepare laminated composites. This present investigation deals with the fabrication and micro-structural investigation of developed composite through friction stir additive manufacturing technique. TiC particles and grinding sludge, an industrial waste was used as reinforced material to develop AA6061/TiC/GS composite material. Optical microscopy, SEM analysis, EDS test and mechanical properties were investigated for the prepared composite. HSS tool having tapered pin tool was considered for the stirring action. Results revealed that no agglomeration of reinforcement particles was noticed for the fabricated material. An improvement in hardness and tensile strength was noticed for the prepared composite. The SEM analysis of FSAM tool before and after welding was also performed. Fractographic analysis was also performed for AA 6061/TiC/GS composite.

This study emphasizes the fabrication and characterization of composites with AA 6063 as the matrix reinforced with a hybrid blend of silicon carbide, graphene, and fly ash particles through the stir casting technique. It seeks to elucidate the extent and improvement of mechanical characteristics of the fabricated composites through the synergistic impacts of these reinforcements. Mechanical tests such as hardness, tensile, impact and flexural tests were conducted for assessing the various properties of the metal-matrix composites. The research further validated that a composition of 4 wt % graphene with SiC and fly ash yielded the greatest improvement in mechanical properties. There is an increase in hardness, toughness, tensile strength, and flexural strength by 27.76, 75.67, 119.23, and 98.88% respectively as compared to undoped graphene samples. The enhanced characteristics may be ascribed to a finer grain structure and a homogeneous distribution of reinforcements. However, samples with 6 wt % graphene led to agglomeration hence there are reduction in the mechanical properties. The findings reveal that the developed hybrid metal matrix composites exhibit significantly enhanced mechanical properties, rendering them suitable for advanced structural applications in industries such as aerospace and automotive.

This study investigates the recycling of industrial waste copper chips generated during the processing of copper chips containing approximately 5% magnesium. An innovative patented modification was integrated with the classical solid-state sintering method to directly produce copper ingots from these wastes. Unlike conventional powder metallurgy techniques, the process employs a low-pressure (7 bar) and short-term (5 minute) sintering step without prior surface cleaning. Initially, the chips undergo pre-compression at 200°C, followed by heat treatment at 1035°C, and subsequently a secondary pressing to yield copper ingots. X-ray diffraction analysis predominantly identified the face-centered cubic copper phase, while energy dispersive spectroscopy indicated only trace amounts of oxygen and iron. The abbreviated sintering duration successfully preserved over 97% of the metallic copper phase and minimized oxide formation. Scanning electron microscopy confirmed a homogeneous microstructure, with crystallite sizes and morphology optimized based on the sintering conditions. This approach offers substantial advantages in terms of energy savings, production efficiency, and environmental sustainability.

The effect of various cooling conditions during quenching on the microstructure and hardness of multicomponent brasses has been studied using the example of brass LMtsAZhKS (CuZn13Mn8Al5Si2Fe1Pb). It has been shown that the use of polymer solutions of different concentrations instead of water makes it possible to increase the hardness and change the structural state of the alloys without significant quenching deformations. The cooling rate in MZM-26 oil and 10% solution is close to critical, which suppresses the decomposition of the β‑phase and fixes its unstable state. During subsequent aging, a significant increase in hardness (up to 120% of the initial) occurs due to the formation of a mixed microstructure with martensite and dispersed phases providing effective hardening. The most effective hardening occurs within one hour of aging. The formation of the microstructure during quenching in polymer media is ensured by the redistribution of diffusion-active elements: aluminum and silicon. Maximal hardness is achieved when the processes of nucleation and growth of the α-phase are suppressed, while during aging, shear and dispersion hardening mechanisms are realized.

In the present paper, the effect of diffusion bonding (DB) and post-bond heat treatment on a microstructure and mechanical properties of a Ti₂AlNb-based alloy VTI-4 was studied. DB was carried out using an SPS 10–3 selective plasma sintering system. The optimum mechanical properties of DB-joints (σ_u = 1240 MPa, σ_0.2 = 1070 MPa, δ = 4.6%) were achieved after DB at temperatures of 940°C and 960°C, a holding time of 120 minutes, and a pressure of 15–25 MPa. The obtained mechanical properties were equal to that of the initial material (σ_u = 1230 MPa, σ_0.2 = 1190 MPa and δ = 3.5%, 400 ± 10 HV_0.2). After DB at 940–960°C, microhardness was 395 ± 30 HV_0.2, which was higher than that after DB at 920°C (360 ± 25 HV_0.2). DB provoked an increase in the volume fraction of the O-phase along the joint interface compared to the base material. Post-bond heat treatment resulted in an additional increase in the volume fraction of the O-phase that increased strength and hardness.

In order to process the low-grade wad clay (Mn 4–6%) which is deposited in the central region of D.P.R of Korea, slurry electro leaching method (diaphragm electrolysis) was applied. The effects of the temperature, current density, ratio of liquid to solid (L/S), time and coagulant agent were observed through the basic experiment on slurry electro leaching of the wad clay. The main condition for the slurry electro leaching was as follows: current density 150–200 A/m², temperature >65°C, L/S = 10 : 1, time 1.1 time of theoretical leaching time and amount of the coagulant agent 50 g/t. Under these conditions, the leaching rate was above 95% and the content of Mn in anodic electrodeposits is 45%. Slime in the wad clay greatly affected the purity of MnO₂ formed on the anode.

Selective laser melting (SLM) technique is one of the most popular advanced manufacturing techniques. The SLM process parameters affect the multiple quality-attributes of the SLM-built parts. The aim of this work is to develop a new optimization methodology of the SLM process parameters for improving the multiple quality attributes of the SLM-built parts. It is a multi-objective optimization (MOO) problem. The multiple quality attributes are converted into a single overall quality index (OQI) using multi atrribute decision making (MCDM) method, and the MOO problem converted into a single objective optimization (SOO) one. The optimization result may differ according to the applied MCDM method. To address it, this work proposed a reasonable process optimization methodology for improving multiple quality attributes of the SLM-built parts using integrated OQI (I-OQI) combined with multiple OQIs obtained from multiple MADM methods. The proposed methodology was applied to optimize the process parameters such as laser power (LP), scan speed (SS) and overlap rate (OR) for improving five quality attributes such as tensile strength, hardness, relative density, volumetric energy density, and build rate of the SLM-built AlSi10Mg alloy. The optimal values of the SLM process parameters obtained from Taguchi and grid search optimization methods were LP of 320 W, SS of 900 mm/s, and OR of 0.25. The methodology could be actively applied to the SLM process optimization for not only Al alloys but also various metal/alloys.