Papers by Keyword: Copper Alloy

Abstract: Alumina dispersion strengthened copper (ADSC) is nowadays well-researched material. Its properties make it an excellent candidate for use in electrical engineering applications such as material for welding electrodes. The subject of this study was a joint of ADSC and precipitation-strengthened Cu-Cr alloy. ADSC was prepared by powder metallurgy method using Spark Plasma Sintering (SPS). While SPS allows the preparation of low porosity compacts it's limited by the size and shape of compacts it can prepare. This work aimed to prepare different joints between ADSC and Cu-Cr alloy and examine their properties as well as chemical composition and microstructures. Three types of joints were tested. A joint made by pressing ADSC into Cu-Cr sleeve shows the forming of oxides in the joint as well as the hardening of Cu-Cr on the contact surface due to deformation strengthening. Joint made by SPS flash sintering showing the formation of relatively big cavities and the formation of oxides on the materials interface. The in-situ joint was produced using a method where a Cu-Cr sleeve replaced the bottom punch in SPS compaction. The In-situ interface shows very little change in chemical composition and seemingly made a diffusion connection. However, these samples show higher porosity of composite compared to regularly SPS prepared compacts.

Abstract: This study uses numerical simulation to examine the influence of variations in laser power and transition zone length on the tensile behavior of bimetallic samples designed to be manufactured by selective laser melting (SLM). The materials studied are 316L stainless steel-copper, chosen for their complementary mechanical properties and functional relevance in high-stress applications. The transition between the two materials was modeled by modulating the laser power according to different profiles (linear, concave or convex) and over different lengths (d(x) = 0 mm, 10 mm, 20 mm) in order to evaluate their impact on the simulated mechanical performance. The numerical results show that a gradual transition in laser power, combined with an extended transition zone, significantly improves stress distribution and leads to better mechanical integrity. Simulations performed in ANSYS provide an in-depth analysis of stress fields and highlight the crucial role of manufacturing parameter management. This study thus highlights the importance of precise control of manufacturing parameters in the 3D printing of bimetallic components and demonstrates, through numerical modeling, that optimized transition management can improve the mechanical integrity of parts produced by SLM. Experimental validation of these results will be an essential prospect for future work.

Abstract: Wire arc additive manufacturing (WAAM) according to ISO/ASTM 52900:2021 is a widely known additive manufacturing process to produce a new 3D part or repair a damaged metal part. Copper-based alloy, i.e., CuAl8, is widely used to repair marine structures and to make bearing overlays due to its excellent corrosion and wear resistance properties. This paper will give an insight into the multi-layer deposition of CuAl8 at different substrate orientations. Furthermore, multi-material deposition, i.e., CuAl8 and mild steel, is investigated, which can help industries to combine the features of both materials and lead to the development of functionally graded materials.

Abstract: The article discusses the influence of the parameters of friction stir welding modes on the formation of the outer surface of the weld and the thickness of the intermetallic layer for the thickness of the welded samples of 3 mm. Changing the rotation speed from 600 rpm to 1000 rpm of the welding tool allows you to control the amount of energy input to transfer the welded material into a superplastic state. The welding speed was varied from 20 mm/min to 80 mm/min. The most optimal mode was for an aluminum and copper alloy with a thickness of 3 mm, a rotation speed of 900 rpm, a welding speed of 25 mm/min, an angle of inclination of 3⁰ at which the mechanical properties of the welded seam approached the most plastic material (aluminum). The article considered thermal cycles measured near the pin from the side of the aluminum and copper alloy. The maximum temperature was 900 K on a copper alloy. The parameters of welding modes also affect the formation of intermetallic layers. If the thickness of the intermetallic layer does not exceed 4-5 μm, then increased values of the mechanical strength of the welded dissimilar joint are observed.

Abstract: This paper is about a comparative analysis of the requirements of the Russian standard, the standard of the European Union and the PRC for overhead contact wires for electrified high-speed railways. New generation contact wires must have a high level of mechanical, electrical and operational properties. The Russian standard does not regulate the chemical composition of alloys used for the contact wires manufacture. Unlike the standards of the European Union and China, the Russian standard regulates the maximum value of the relative creep. Compositions, mechanical properties, electrical resistivity and recrystallization temperature for the contact wires with a cross section of 120 mm² are given. The requirements for the material for the contact wire are presented. The need to use more durable conductive materials instead of copper is noted since mechanical loads and operating temperatures are constantly increasing. The values of mechanical properties, recrystallization temperature and creep of contact wires made of copper alloys are given. Based on the analysis results of the literature data and the experiments, alloys of the Cu-Mg system are recommended as a material for the contact wire manufacture for an overhead network system for high-speed railways.

Abstract: The investigation of new materials that have properties such as resistance to high temperatures, wear resistance, rigidity, and low weight, involves the use of technological processes with more and more advantages. For this purpose, mechanical alloying is a widely used technique, which consist of high-energy impact between balls inside a container, where constant collisions deform and fracture the material, achieving the alloy of the particles in a solid state. This work focuses on the Vickers hardness evaluation of the copper matrix alloy with 4% Pb, 4% Sn and 4% Zn, in an oxidizing atmosphere, sintered at 800 °C and 900 °C, using milling times of 3 hours, 6 hours and 9 hours. The results show that there is a relationship between the hardness obtained, in the two groups of specimens at 800 ° C and 900 ° C, with the grinding time and the sintering temperature, among others used in the process. An average maximum hardness of 53.4 HV was obtained.

Abstract: Nickel aluminum bronze (NAB) castings possess favourable combinations of strength and resistance to corrosion, biofouling and cavitation/erosion, and so have long been used in naval applications. Nonetheless, in seawater environments NAB castings are susceptible to selective phase corrosion and so such components periodically require either replacement, which is very costly, or repair. However, repairs involving traditional, high heat input welding operations can lead to distortion and microstructural changes that unacceptably degrade NAB corrosion performance, and so repairs are not commonly performed. In the present work, cold spray is explored as an alternative for NAB (alloy CuAl9Fe5Ni5) repair without excessive distortion or base metal degradation, and preliminary results of its performance reported. Suitable cold spray parameters have been determined using an iterative approach by analyzing deposits in terms of microstructure, porosity and adhesion to the substrate. It is intended that these parameters will later be used to create simulated repairs which can be more thoroughly characterized for strength, toughness and corrosion performance.

Abstract: In general, a flux is used to braze a copper alloy. In many cases, when the molten brazing filler metal spreads in the set joint gap, vaporised flux and its residue are produced, and defects (mainly voids) are formed. Voids, which are formed on the brazed layer, cause deterioration in the strength and other properties. However, with conventional evaluation methods (e.g. ultrasonic or X-ray radiography tests), the behaviour of the molten brazing filler metal during the brazing process cannot be visually observed from the outside of the joint. Therefore, the void formation process cannot be clarified. To improve the quality of the brazed layer, it is necessary to elucidate the mechanism of void formation. The purpose of this study is to observe the behaviour of the molten brazing filler metal by performing an X-ray radiography test at the same time as brazing and to study how to reduce voids. In this study, a brass specimen was brazed with a Cu–P-based brazing filler metal. The specimen was brazed by heating in an electric furnace, and the specimen was irradiated with X-rays. The state where the molten brazing filler metal spread into the gap was photographed as the transmission image. Thereafter, the behaviour of the molten brazing filler metal was analysed.

Abstract: A 2-D finite volume Computational Fluid Dynamic (CFD) model, using Ansys Fluent vR.1 of a vertically oriented upwards continuous casting (VUCC), was investigated for 8 mm, oxygen free copper (OFCu). The simulations enabled the mapping of the cast OFCu solidification front (SF) interface from liquid to solid. Optimisation of the simulation parameters were investigated which included mesh size and the Ansys specific ‘mushy zone’ constant (A_mush), which is used to account for fluid flow dampening at SF within the model. Observations of the SF, the change in fluid volume in the die, the simulation convergence and the total simulation time, revealed that the optimised casting parameters were for mesh size 1×10^-4 m and A_mush 10⁶ kg/m³s. These parameters were compared with the cast rod and highlighted qualitatively the relationship between grain growth direction and SF position during a casting pulse cycle.

Abstract: Stress-controlled fatigue tests were conducted on round-bar specimens to understand the fatigue behavior of precipitate-strengthened Cu–6Ni–1.5Si alloy. The cracks were initiated at the grain boundaries, followed by growth along the crystallographic slip planes in the adjacent grains. The crack growth data of plain specimens exhibited a large scatter, resulting in a difficulty of the measurement of crack growth rate. To evaluate the small-crack growth rate of the alloy, the plain specimens with a small blind hole as the crack starter were fatigued. The crack growth rate of small cracks from the hole was uniquely determined by a term σ_a ⁿl and the material constant, n, was 5.3. The term σ_a ⁿl with n = 5.3 was applied to the plain specimen, showing good applicability of the term to small cracks in the plain specimen.