Abstract: This work focuses on welding repair of aluminium alloy 6082 T6 by TIG welding process. Two types of filler, 4043 and 5356 were used. A comparison at I= 120A,140A, welding speed 20cm/min and gas flow rate 15 L/min was studied. Physical characteristics, macrostructure and microstructure at weld metal and Heat Affected Zone (HAZ) were investigated. Which at 140A can welding repair. The parameter 140A have complete melting and fail area at HAZ and mechanical properties more than 120A.
Abstract: The repair welding of aluminium alloy 6082T6 with two fillers 4043 and 5356 were studied by using MIG welding process with pulse current at frequency 5 Hz. After that, macrostructure and microstructure were investigated and the density of porosity and testing of mechanical properties were determined. The results found that the density of new weld was less than repair weld. The results of mechanical tests showed that the new weld were better than the repair weld.
Abstract: The objective of this study is to investigate the effect of adding some alloying elements (including iron, aluminum, chromium, cobalt, and titanium) to 90 wt. % copper – 10 wt. % nickel alloy on the hardness property. Copper-nickel synthetic alloys were prepared in an induction furnace, in an argon/7% vol. hydrogen atmosphere in cylindrical boron nitride crucibles. They were then homogenized at 950°C for 10 hours in the same protective atmosphere. Vickers hardness measurements, microstructure examination, and Energy Dispersive Spectrometry (EDS) mapping analysis were performed for all synthetic alloys. Hardness measurements results show that the addition of all the alloying elements used in this investigation improve the hardness of the 90 wt. % copper – 10 wt. % nickel alloy. It was concluded that the aluminum was the most effective alloying element on the hardness value for 90 wt. % copper – 10 wt.% nickel alloy.
Abstract: Laser ablation under a flowing water layer can reduce thermal damage in work material and also provide a better machining performance than processing in ambient air. However, there is still a lack of insight into a more complicated process like laser milling operation in water. Besides the laser parameters, the roles of water flow direction on the cut geometries need to be elucidated to realize the viability and reliability of the laser milling process in water. This study is for the first time to reveal the effects of water flow direction on the cavity dimensions and cut surface roughness in the laser milling process performed under a flowing water layer. Titanium alloy was used as a work sample in this study. The experimental results indicated that the laser beam should travel in the same direction of water flow to provide a uniform cavity depth and smooth milled surface.
Abstract: Wire electrical discharge machining is a material removal process of electrically conductive materials by the thermo-electric source of energy. This kind of machining extensively used in machining of materials with highly precision productivity. This work presents the machining of titanium alloy (TI-6AL-4V) using wire electro-discharge machining with brass wire diameter 0.5mm.The objective of this work is to study the influence of three machining parameters namely peak current, pulse off time and wire tension to cutting rate, material removal rate, surface roughness and kerf width followed by suggesting the best operating parameters towards good machining characteristics. A full factorial experimental design was used with variation of peak current, feed rate and wire tension, with results evaluated using analysis of variance techniques. Parameter levels were chosen based on best practice and results from preliminary testing. Main effects plots and percentage contribution ratios are included for the main factors and their interactions.
Abstract: Aluminum alloys are used widely in many applications due to its low in density which can lead to a lightweight product. A high percentage of Cu in the chemical composition of the 2024 aluminum alloys helps withstand the occurrence of corrosion as well. Thus, aluminum alloy grade 2024 is used as a material for several parts in aircraft and spacecraft components, (e.g. the body of commercial airplanes), as well as parts in many other applications. Gas Tungsten Arc Welding (GTAW) is used widely in joining material parts together. Inappropriate welding parameters usually cause problems such as porosity in the welding. The occurrence of porosity is undesirable in welding because it can affect the strength of the welding area as well as other properties. Tensile residual stress near the surface of the material expedites the fatigue crack initiation. The relationship of porosity and residual stress for GTAW parts was very limited in literatures. Therefore, the objective of this research was to investigate the relationship of porosity to the occurrence of residual stress after the welding process. Full factorial design of experimental technique was used for setting up welding conditions of the GTAW. The specimen with highest porosity was selected for further analysis of its effect on residual stress. Porosity was analyzed by the radiographic testing (RT) and the residual stress was measure by X-ray diffraction (XRD) using sin2 method. The results showed that the highest porosity in the welded bead was found at the current of 130 A, the welding speed of 210 mm./min., and the wire feed rate of 700 mm./min. The results also suggested that lower current and welding speed caused an increase in porosity. The residual stress results on both longitude and transverse directions showed tensile residual stress at locations around the welded bead area.
Abstract: The effect of precipitate on microstructure evolution and hardness of Al-Cu alloy during torsion deformation has been investigated, by comparing the evolution of microstructure in aged Al-2wt.% Cu alloy with commercial purity aluminum (1100Al). The microstructure evolution is studied by Transmission Electron Microscopy and Electron Backscatter Diffraction, and hardness is measured using Vickers hardness measuring instrument. It is found that the presence of precipitate enhance the grain refinement and hardness of Al-Cu alloy. By applied equivalent strain of 3.26, the (sub) grain size of 86 nm is achieved. In contrast, the presence of precipitate is found to be inhibiting the development of high angle grain boundary.
Abstract: Magnetocaloric effect (MCE) in the vicinity of first order martensitic transformation and second order magnetic transition in a single crystalline Ni2.13Mn0.81Ga1.06 Heusler compound was studied by a direct method. The obtained results revealed that, for the applied magnetic field strength μ0H = 1.9 T, MCE is irreversible in the vicinity of the first order martensitic transformation only when the MCE measurements are performed under cooling protocol. Plot of the experimentally measured adiabatic temperature change ΔTad as a function of temperature T indicated that ΔTad has a negligible benefit from the magnetic field-induced conversion of the high-temperature austenitic phase into the low-temperature martensitic phase and is mainly determined by the paraprocess of the austenitic phase around both direct and reverse martensitic transformations.
Abstract: The effect of steel strip-feeding ratio and superheat degree of molten steel on density and segregation of casting ingot is investigated by an original position analysis. It indicates that under the same degree of superheat condition, with the increase of feeding ratio, the average density of the casting ingot increases and the central segregation of the ingot decreases. Under the same feeding ratio conditions, the density and the central segregation increase with the increase of the degree of superheat.