Aiming to reduce the weight of components, thus allowing a profit in terms of energy saving, automotive industry as well as aircraft industry extensively uses aluminum alloys. The most widely used joining technology in aircraft industry is riveting, while welding seems to be used in the car industry in the case of aluminum alloys. However, welding technology is characterized by many defects, such as gas porosity; oxide inclusions; solidification cracking (hot tearing); and reduced strength in both the weld and the heat affected zones which could limit its development. Many techniques are used for aluminum alloys welding, among them is electron beam welding (EBW), which has unique advantages over other traditional fusion welding methods due to high-energy density, deep penetration, large depth-to-width ratio, and small heat affected zone. The welding parameters that yield to optimal weld joint have been previously obtained. These optimal parameters were validated by welding a specimen using these parameters. To evaluate this optimal weld joint, complete, microstructural observations and characterization have been carried out using scanning electron microscopy, optical microscopy, and energy dispersive X-ray analysis. This evaluation leads to description and quantification of the solidification process within this weld joint.

Aluminum alloys are the subject of increasing interest in the automotive, as well as aircraft industries. Concerning the assembly, welding was extensively applied in the car industry. Nevertheless, welding defects generated during the process result in reduction in strength of both the weld; and heat affected zone which could limit its applications. Electron beam welding (EBW) has unique advantages over other traditional fusion welding methods due to its high-energy density, deep penetration, large depth-to-width ratio and the resulting very small heat affected zone. Optimization of EB welded joint of 2219 Al-alloy, from the yield strength, hardness and bead geometry point of view, is the topic of this study. Taguchi methodology with grey relation analysis has been applied to find the optimal welding parameters for welding of a sheet of the mentioned aluminum alloy with electron beam. The optimal welding parameters have been selected and verified experimentally.

The objective of this experimental study is to investigate the effect of the main compaction and sintering parameters on the micro-structure and the mechanical properties of the liquid phase sintered 93%wt.W-4.9%wt.Ni-2.1%wt.Fe tungsten heavy alloy aiming at determining the optimum values of these parameters. Elemental powders were mixed using planetary mixer for 5 hours to ensure suitable homogeneity. Uni-axial compaction was applied to obtain standard tensile and impact specimens using compaction pressures ranging from 50MPa to 300MPa. Vacuum liquid phase sintering was carried out under different temperatures from 1460 ᵒ C up to 1500 ᵒ C and sintering time from 30 minutes up to 120 minutes. The effect of these parameters was characterized in terms of density, hardness, impact resistance and tensile properties. Microstructure variations, notably grain size, matrix volume fraction and contiguity were measured and used to explain the effect of sintering temperature and time on the properties. The obtained results indicated that optimum hardness and impact resistance can be obtained at a compaction pressure of about 200 MPa. As the sintering temperature increases, the grain size and volume fraction of matrix increase, while the contiguity decreases. As a result of these micro-structural changes, strength and hardness decrease. On the other hand, ductility and impact resistance increase with sintering temperature to some maximum at 1480 ᵒ C. At further increase of this temperature, grain growth becomes the dominant factor leading to a sensible decrease in all properties. The effect of sintering time on mechanical properties is related to grain growth and pore coarsening mechanisms. It is generally observed that strength and ductility decrease after sintering over 90 minutes at 1480 ᵒ C. It was also noticed that the ductility is more sensitive to sintering time and is reduced sharply with prolonged holding at the sintering temperature. It can be concluded that the mechanical properties of tungsten heavy alloys are sensitive to the processing cycle and are adversely affected by residual porosity. Moreover, tungsten grain size plays an important role in dictating the failure mode during tensile testing. If tungsten grain size is large interface failure is predominant. However, as the grain size decreases, fracture mode changes gradually from interface failure to matrix failure and then to tungsten grain cleavage failure.

Aluminum's unique properties, e.g. light weight, high strength, and resistance to corrosion, make it an ideal material for use in conventional and novel applications. Aluminum has become increasingly used in the production of aerospace equipment, automobiles and trucks, packaging of food and beverages. However it suffers from poor joint strength when welded by conventional fusion welding. In this investigation an attempt has been made to improve the welded joint strength through using of electron beam welding (EBW). Due to special features of EBW, e.g. high energy density and accurately controllable beam size and location, in many cases it has proven to be an efficient method for joining difficult to weld materials. In this paper, the effects of EBW parameters on the ultimate tensile strength (UTS) has been investigated, The experiments were based on one-variable-at-a-time (OVAT) method,

This paper presents the optimization of welding parameters of electron beam welded joint of dissimilar materials namely AISI 304 stainless steel and AISI 1020 low carbon steel (0.21% C.). Three main welding parameters were investigated. These parameters are welding current, focusing current, and welding speed. The optimization was based, from one hand, on microstructure analysis of both bead and heat affected zones, using optical and scanning electron microscopes, and, from the other hand, the evaluation of tensile, impact, and micro-hardness mechanical properties. The results of the investigation showed that, an optimum welding current of 19 mA, a focusing current of 875 mA, and a welding speed of 8mm/s at a working distance 100 mm can provide uniform welding bead with full penetration, without undercuts and a narrow width of HAZ in the order of 2.3 mm. Moreover, they can secure a tensile failure outside the joint, in the base metal (low carbon steel) satisfying a tensile strength of about 430 MPa. Furthermore, the impact resistance of the joint was found to provide about 160 J/cm 2 (hummer against the root of bead) and about 70 J/cm 2 (hummer against the face of bead). The hardness distribution along the joint from the stainless steel side to the low carbon steel side through the bead and HAZ was determined, and indicates that, a maximum hardness of about 380 HV was obtained in the center of the bead. This value is higher than the obtained hardness values of both the austenitic stainless steel and low carbon steel.