Development and Evaluation of the Ultrasonic Welding Process for Copper-Aluminium Dissimilar Welding

The demand for joining dissimilar metals has exponentially increased due to the global concerns about climate change, especially for electric vehicles in the automotive industry. Ultrasonic welding (USW) surges as a very promising technique to join dissimilar metals, providing strength and electric conductivity, in addition to avoid metallurgical defects, such as the formation of intermetallic compounds, brittle phases and porosities. However, USW is a very sensitive process, which depends on many parameters. This work evaluates the impact of the process parameters on the quality of ultrasonic spot welds between copper and aluminium plates. The weld quality is assessed based on the tensile strength of the joints and metallographic examination of the weld cross-sections. Furthermore, the welding energy is examined for the different welding conditions. This is done to evaluate the influence of each parameter on the heat input resulting from friction at the weld interface and on the weld quality. From the obtained results, it was possible to optimise parameters to achieve satisfactory weld quality in 1.0 mm thick Al–Cu plate joints in terms of mechanical and metallurgical properties.

Effect of Pouring Temperature on Microstructures and Mechanical Properties of 7085 Ingot Casting by Finite Element Analysis

The microstructure and mechanical properties of the 7085 ingot casting was tested by OM, SEM and EDS, the fatigue damage was observed in the driving test process, the temperature gradient distribution was adjusted observably by using the FEM simulation analysis. By adjusting the pouring temperature, many micro shrinkage metallurgical defects were eliminated, the tensile strength, yield strength and elongation were raised to 498MPa, 362MPa and 7.4% at the T6 heat treatment state.

Виготовлення авіаційних деталей з жароміцних нікелевих сплавів методом адитивного плазмового наплавлення

The aviation part of the ring-type was made of heat-resistant structural alloy EI 868 (HN60VT) by the method of additive multilayer plasma surfacing with wire. The traditional technology for obtaining this type of ring blank is the stamping of rods, which are then brought to the final shape of the part by further machining. The disadvantage of traditional technology is the significant cost of metal, which in the process of machining the pressed rod, is converted into chips and not reused, which increases the cost of the finished product. The use of additive technologies will significantly reduce the cost of material in obtaining annular workpieces by manufacturing a workpiece with a configuration as close as possible to the geometry of the part. Additive surfacing was performed on a robotic complex consisting of a plasma power supply SBI PMI-350 AC/DC TL and work FANUC M-710iC on a rigidly fixed substrate of steel 20. To determine the possibility of obtaining aviation parts using the method of layer-by-layer plasma surfacing, a study of the deposited material was conducted The structure of the grown part was studied, it was found that the microstructure corresponds to the normal state of the alloy EI868 (HN60W) in the microstructure of the fusion line is not visible, the structure is homogeneous with the mutual germination of grains between layers. Alloy parts obtained using the method of additive cultivation are at the level of cast blanks and forgings and at T = 900oC are: sв =35±5 кгс/мм2,s0,2 =49±5 кгс/мм2, y = 62±5 %. After machining the grown workpiece, a capillary method of control and radiation control of the grown part - cracks and other types of critical metallurgical defects was not detected. The practical significance of the introduction of this method is a significant reduction in material costs in obtaining parts and ensuring economic efficiency, which is about 159 thousand hryvnias.

Selective Electron Beam Melting (SEBM) of Pure Tungsten: Metallurgical Defects, Microstructure, Texture and Mechanical Properties

Effects of processing parameters on the metallurgical defects, microstructure, texture and mechanical properties of pure tungsten samples fabricated by selective electron beam melting (SEBM) are investigated. SEBM-fabricated bulk tungsten samples with features of lack of fusion, sufficient fusion, and over-melting are examined. For samples upon sufficient fusion, an ultimate compressive strength of 1.76 GPa is achieved at the volumetric energy density of 900 J/mm 3 ~1000 J/mm 3. The excellent compressive strength is higher and the associated volumetric energy density is significantly lower than corresponding reported values in literature. The average relative density of SEBM-fabricated samples is 98.93%, and no microcracks but only pores with diameters of few tens of micrometers are found in SEBM-ed tungsten samples of sufficient fusion. Properties of samples by SEBM and selective laser melting (SLM) have also been compared. It is found that SLM-fabricated samples exhibit inevitable microcracks, and have a significantly lower ultimate compressive strength and a slightly lower relative density of 98.51% in comparison with SEBM-ed samples.

A Micro-Computed Tomography Comparison of the Porosity in Additively Fabricated CuCr1 Alloy Parts Using Virgin and Surface-Modified Powders

Recently, the use of novel CuCr1 surface-modified powder for reliable laser powder-bed fusion (LPBF) manufacturing has been proposed, enabling a broader LPBF processing window and longer powder storage life. Nevertheless, virgin CuCr1 powder is also LPBF processable, on the condition that a high-energy density is employed. In this work, we compare two dense specimens produced from virgin and surface-modified CuCr1 powder. Furthermore, a third sample fabricated from surface-modified powder is characterized to understand an abnormal porosity content initially detected through Archimedes testing. Utilizing high-resolution micro-CT scans, the nature of the defects present in the different samples is revealed. Pores are analyzed in terms of size, morphology and spatial distribution. The micro-CT data reveal that the virgin CuCr1 dense specimen displays keyhole pores plus pit cavities spanning multiple layer thicknesses. On the other hand, the sample fabricated with the surface-modified CuCr1 powder mainly contains small and spherical equi-distributed metallurgical defects. Finally, the CT analysis of the third specimen reveals the presence of a W contamination, favoring lack-of-fusion pores between subsequent LPBF layers. The LPBF melting mode (keyhole or conductive), the properties of the material, and the potential presence of contaminants are connected to the different porosity types and discussed.

About Some Reasons of Destruction of Gear Details of the Car

It is shown that deformed steel has an advantage over cast steel in terms of mechanical properties. It was revealed that the decrease in the durability of gear parts is associated with the presence of metallurgical defects in the steel. The square segregation is always inherited by the finished part and its appearance on the surface leads to the destruction of the product. The dendritic structure of steel is the reason for the low endurance strength of the tooth of the part. For heavily loaded gear parts of the «shaft-gear» type, it is recommended to use rolled products with a high degree of crimping (extension). To eliminate the dendritic structure in steel, hot deformation of the metal can be carried out at the stage of forging production.