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.

Mechanical and Micrography Analysis of Armour Plate Weldment Using Tungsten Inert Gas and Oxy-Acetylene Welding Methods

Defence Industries Corporation of Nigeria (DICON) has compared the effect of Tungsten Inert Gas (TIG) and Oxy-Acetylene welding methods on microstructural and some mechanical properties of Armour plate for the modification of military troop carriers. The optical emission spectrometer (OES) at DICON was used to analyse the chemical composition of the armour plate strip. It was then machined and cut to various test piece dimensions for both welding processes, following which the weldment samples were subjected to post-weld mechanical tests (tensile, impact, and hardness) and metallographic examination. The samples were then welded according to the procedure outlined in this study. The fundamental composition of armour plates was preserved in the samples. When compared to Oxy-Acetylene (OA) welding, Tungsten Inert Gas (TIG) welding produced better results, with an average ultimate strength (UTS) of 603.52 MPa and an impact strength of 10.53 J. In addition, the TIG analysis hardness strength for the source material, heat affected zone (HAZ), and weldment sample is 510.3, 502, and 511-HV, respectively. At x200 magnification, the micrography of the TIG weldment revealed a small coarse grain size of ferrite and larger areas of pearlite.

Investigation of the Relationship between Degradation of the Coating of Gas Turbine Blades and Its Surface Color

This article presents issues concerning the relationship between the degradation of the coating of gas turbine blades and changes in the color of its surface. Conclusions were preceded by the determination of parameters characterizing changes in the technical condition of protective coatings made based on a metallographic examination that defined the morphological modifications of the microstructure of the coating, chemical composition of oxides, and roughness parameters. It has been shown that an increased operating time causes parameters that characterize the condition of the blades to deteriorate significantly. Results of material tests were compared with those of blade surface color analyses performed using a videoscope. Image data were represented in two color models, i.e., RGB and L*a*b* with significant differences being observed between parameters in both representations. The study results demonstrated a relationship between the coating degradation degree and changes in the color of the blade’s surface. Among others, this approach may be used as a tool to assess the condition of turbine blades as well as entire gas turbines.

Characterisation of the Microstructure of Plain Carbon Steel Formed during Isothermal and Continuous Cooling Following Austenitisation

The present study has been undertaken to compare the microstructure of the plain carbon steel, containing 0.65 carbon, which was formed during varying isothermal and continuous cooling conditions following austenitisation at the same temperature and soaking time. After austenitisation, one set of samples was subjected to isothermal treatment which was carried out at a temperature varying in the range of 650–400 °C, and the other one was continuously cooled to ambient temperature using different cooling rates ranging from 500 to 1.4 °Cs–1. The metallographic examination of the samples was fulfilled using light and TEM microscopy. Additionally, Vickers hardness measurements were performed.

Influence of Plasma Electrolytic Oxidation coating on corrosion characteristics of Friction Stir Welded ZE41 rare earth Magnesium alloy

Magnesium and its alloys are extensively used in the defence, aerospace and automotive industries, owing to their excellent mechanical properties. But there is a requirement of corrosion prevention treatment before using it for applications, since the corrosion resistance of Mg alloy is poor. In this work, a study on the mechanical properties of friction stir welded ZE41 rare earth magnesium alloy thick plates of 15mm and 25mm, was carried out. A metallographic examination and mechanical tests were conducted on both the welds. Furthermore, Plasma Electrolytic Oxidation (PEO), a surface conversion treatment was carried out on both the base material as well as on the friction stir butt joints. X-ray diffraction and scanning electron microscopy analysis were carried out on all the samples, with and without coating. The coated and uncoated samples were assessed by potentiodynamic polarisation (PDP) tests and electrochemical impedance spectroscopy (EIS) to study the electrochemical corrosion behaviour. An outer porous layer and an inner dense layer, have been identified from the SEM images. From the corrosion tests results it was revealed that there was an improvement in the corrosion resistance of both the base metal as well as the weldments by the PEO coating process.

Short-Term Creep-Rupture Behaviour of AISI 310S Austenitic Stainless Steel Sheets Manufactured in Salem Steel Plant, a Special Steels Unit of Steel Authority of India Limited, Ministry of Steel, Government of India

The creep behavior of AISI 310S stainless steel taken from SAIL’s Salem stainless steel plant has been investigated by constant load tensile creep test at the temperatures of 973, 1023, and 1073 K and loads of 66.6, 74.8, 86.6, and 94.8 MPa. It exhibits steadystate creep behavior in most test conditions. The double logarithm plot of rupture life and applied stress yielded straight lines at all the three test temperatures indicating that power-law creep due to dislocation climb is the operating mechanism of creep deformation. Linear relationship was obtained for plots of logarithm of rupture life against inverse temperature obeying Arrhenius type of temperature dependence with activation energy of 340 kJ/mol. The stress-rupture data yielded a master curve of Larson-Miller parameter. The plot of Monkman-Grant relationship is typical indicating that rupture is controlled by growth of grain boundary cavities. The metallographic examination of crept samples revealed formation of grain boundary voids and cracks leading to intergranular creep fracture. Deformation twins and carbide precipitates were also observed. Creep-rupture properties are compared with that of AISI 600 ironbased superalloy to analyze quantitatively its behavior

Carburized Layer Cracking Analysis of Counterweight Blocks of Speed Controller

Trace and fracture analysis, metallographic examination, residual stress testing, and material analysis were carried out, coupled with examining the failure timeline, to analyze the cracking problem of 12CrNi3A steel counterweight blocks under multi-factor coupling. The results show that the cracks of the counterweight blocks are intergranular microcracks in the carburized layer and they are delayed cracks under the joint action of microstructure stress, grinding stress and hydrogen. The delayed cracking of the counterweight blocks is mainly related to abnormal hydrogen absorption during surface treatment and poor grinding quality. The obvious microstructure segregation in raw material and the thicker carburized layer promoted the cracking. The following measures should be comprehensively taken to prevent such failure: strictly controlling raw material quality, hydrogen absorption and stress, as well as increasing the processes to remove hydrogen, reduce stress and stabilize microstructure.

Microstructural Examinations of Copper Antimony Alloys

Among other materials, fahlores were used in the Bronze Age copper ore smelting process. These contain, apart from sulfur, arsenic and antimony. Therefore, these elements can be found in Bronze Age copper casting ingots or artifacts. In order to study the behavior of Sb more closely, two copper alloys containing 10 and 30 wt. % Sb were melted and subjected to a metallographic examination. On the one hand, microstructures with copper dendrites and homogeneous interdendritic areas primarily composed of intermetallic phase could be found. On the other hand, at higher Sb concentrations, first Cu3Sb precipitated which, in turn, transformed to Cu10Sb3 upon cooling. The crystals in these microstructures were characterized by numerous parallel cracks. No further phases were observed by XRD.

AĞ VEYA İP TIRMANMALI OYUN GRUPLARINDA KULLANILAN HALATLARIN ÜRETİLMESİ İLE İLGİLİ YENİ BİR YÖNTEM

Nowadays, climbing game tracks are available for children and for young people and adults. Some of these game tracks are climbing tracks designed as a net. Other ones are climbing groups comprising ropes and similar structures that are suitable for gripping by the hand. There are also game tracks that include both basic game tracks or have different designs while maintaining the fundamental characteristics. However, their common characteristic is that they allow people to try to grasp the rope or net tightly and play or do exercise with an experience close to the natural environment. For this reason, yarns (strings) made of materials such as nylon, polypropylene or polyester are either directly knitted or adhered with chemical adhesives on steel wires. However, during its use, the knitted or adhered yarns (strings) on the steel wire are opened, disorganized or worn. This causes the wires to corrode and / or wear under ambient conditions and thus shorten the life of the ropes. In this study, a solution has been developed to provide a rigid coating of these yarns on the wires. In our study, after the threads were wound on the wires, the steel wires were heated by an electromagnetic induction current and thus, the threads on the steel wires were softened with the effect of the heat. Then, during cooling, the threads harden and partially adhere to each other. Due to this heating process, the temperature was kept under control in order to prevent the properties of the steel wires from deteriorating. After the wires were produced, they were tested with tensile test, hardness and metallographic examination methods, and changes in their properties were controlled.