The relatively new solid state welding process friction stir welding (FSW) was applied in this research work to join similar and dissimilar aluminum ALLOYs AA5754-H22 and AA6063-T4. Different welding rotational speed and transverse speed applied. The joint which was fabricated using tool rotational speed of 2000 rpm and transverse speed of 4 mm/min yielded the best mechanical properties. Soundness of joint was proved by non-destructive tests such as visual inspection and radiography. The global mechanical behavior of the similar welds is very similar to that of the base material. For dissimilar weld important losses in ductility was reported. Microstructural evaluation of fractured surface showed that ductile fracture was the major fracture mechanism of similar and dissimilar welds.

The process of interference fit and bolt clamping force are two effective techniques for improving the fatigue life of the joints and are used in various industries, especially in aerospace and automotive. Most of the previous studies have investigated separate effects of the interference fit and bolt clamping force on the fatigue life of the specimens. In the present research fatigue behavior of interference fitted specimens combined with bolt clamping force has been investigated yet. On the other hand, the pervious researches on the interference fit and bolt clamping force have been studied at laboratory temperature and the effect of temperature changes has not been investigated. To investigate the effect of temperature on the fatigue life of specimens, two different temperatures (i. e. 60° C and 120° C), aside from room temperature, were selected and fatigue life of specimens are studid at these tempratures. The fatigue tests were performed on the specimens of Al-ALLOY 7075-T6 ALLOY to obtain S-N data.

In this study, microstructure and mechanical properties of diffusion joints between 5754, 6061 and 7039 aluminum ALLOYs and AZ31 magnesium ALLOY were investigated. Diffusion joints were done between the ALLOYs at 440 °C, for duration of 60 minutes, at 29 MPa pressure and under 1×10-4 torr vacuum. The interface of joints was studied using optical (OM) and scanning electron microscopy (SEM) equipped with EDS analysis and the line scan. According to the results of EDS analysis, the presence of intermetallic compounds including Al12Mg17, Al3Mg2 and their mixture was observed at the diffusion zone. Also, according to the results of the line scan, the hardness value of aluminum ALLOYs has a considerable effect on diffusion of the magnesium atoms toward aluminum ALLOY and the greatest diffusion of magnesium was observed when 6061 aluminum ALLOY was used. More diffusion resulted in a stronger bond between atoms of magnesium and aluminum, and maximum strength of approximately 42 MPa was obtained when 6061 aluminum ALLOY was used.

The most important defect in casting of Al-5Cu-1Ag ALLOY is hot tear. To solve this problem, using new casting methods such as semi-solid casting process is in forth. In this research after ALLOYing process, samples were casted via common direct casting (DC) and semisolid casting (SC) methods. These samples were aged for 18 hours at 150oC. Microstructural studies were performed by optical and scanning electron microscopes equipped by EDS for elemental analysis and image analyzing by CLEMEX software. Mechanical properties were investigated by the use of Brinell hardness and tensile strength measurements results. Study on semi-solid behavior and determination of optimum solid fraction were performed by Thermo Calc Software. Results show that the dendritic structure in DC casted samples has changed to a 78% spherical structure with 48 mm diameter in SC method. Thus, hardness, tensile strength and elongation increased up to 50%, 20 % and 77 %, respectively. According to thermodynamically modelling results the optimum temperature range for rheocasting of Al-5Cu-1Ag ALLOY is 545-612oC.

The aim of current research was to examine the texture of annealed Al-7075 ALLOY that develops during Equalchannel angular pressing (ECAP) in different ECAP routes. After annealing heat treatment, the material was pressed up to 4 passes by route A and BC at room temperature. The effect of copper tube casing on the texture evolution was also investigated. The texture was studied by X-Ray diffractometer in ED-plane as well as TD-plane. The qualitative and quantitative analysis of the texture reveals that the texture of the first pass is relevant to initial texture, but by increasing pass number this dependency disappears and the texture is mainly relevant to processing route. The texture calculation by Labotex software shows that the results in both TD (z) and ED (x) planes are in good agreement and covering the specimens with copper tube causes a decrease in texture strength and microstructure inhomogeneity of the specimens.

Zinc based ALLOYs of the Binary system of Zn-Al have wide industrial applications, such as Bearing and Bushing. Various physical metallurgical principles of Zinc-rich ALLOYs have been fully investigated especially, their phase transformations near the room temperature. Less attention has been paid to the Al-rich ALLOY (with more than 20 wt% of Zn) of the same Binary system, especially quench - ageing processes, near the room temperature. In the present article, the phase transformations of the Al based ALLOY (with 30 Wt% of Zn) after the quench- ageing processes, natural and artificially aged at 100°C have been investigated, by mans of Electron Microscopy (T.E.M, S.T.E.M), Techniques. It has been shown that the high temperature supersaturated α' phase is transferred to the stable η- phase by the formation of G.P Zones and two transitional phases called α'm and α"m both with the F.C.C structures.

Plasma Electrolytic Oxidation (PEO) method was employed to enhance corrosion resistance of 7075 Aluminum ALLOY. The coating process carried out in a silicate based electrolyte by DC constant current density. Characteristics of coating were evaluated by X-ray diffraction and scanning electron microscopy methods. Analysis showed the formation of g-alumina oxide film, which has a porous surface and some pores in its structure. Coating corrosion behavior was evaluated by electrochemical tests after 1 hour immersion in 1M H2SO4. Tafel Polarization test revealed that PEO decreased the corrosion current density as ten orders of magnitude, and increased the charge-transfer resistance as twenty five order of magnitude, and thus improved corrosion resistance of 7075 Al ALLOY. Electrochemical Impedance spectroscopy (EIS) test revealed that the coating formed a physical barrier against the charge transfer, and decreased the diffusion rate of the corrosive solution due to its non-columnar structure.

The effects of erbium (Er) addition at various weight percentages (0-0.6 wt.% at an interval of 0.2) on the microstructural characteristics, tensile response and wear properties of as-cast Al-7.5Si-0.5Mg ALLOY were evaluated. The microstructure of samples was examined by X-ray diffraction, optical microscopy and scanning electron microscopy. The obtained results demonstrated that the incorporation of erbium obviously decreased the α-Al grain size and eutectic Si, and altered the Si morphology from plate to semi-globular. Further addition of erbium (> 0.2 wt.%) did not alter the eutectic morphology and size. Moreover, the Al3Er phase was also observed in the eutectic region after modification. Out of the erbium contents used, 0.2 wt.% erbium showed the best influence on the tensile and wear properties. Compared with those of unmodified specimen, the values of ultimate tensile strength and elongation were enhanced by 31% and 39%, respectively with the introduction of 0.2 wt.% erbium. Additionally, a remarkable enhancement in the wear properties was observed with the addition of 0.2 wt.% erbium.

The bobbin tool is a new design of the friction stir welding tool that provides the opportunity of the simultaneous double sided welding. The present research aims to design and manufacture a floating bobbin tool; the capability of which is examined through welding aluminum ALLOY 6061. The results indicated that the high quality and defect-free butt welds can be produced via this tool. Moreover, the strength of the welds is similar to the strength of welded samples done by the conventional friction stir welding method. Regarding the quality and strength, the obtained samples were investigated by mechanical tests including tensile strength test and hardness test. Obtaining 60. 7% joint efficiency is indicative of success in the friction stir welding process; and, thus the efficiency of the designed tool. Besides, the second major characteristic of welding is the hardness, which is due to the dissolution of sediments, is decreased in the stirred area. This finding is confirmed by the behavior reported by the other investigators in the literature.

Aluminum ALLOYs, due to their high variety and favorable mechanical properties, are widely used in industries. Aluminum ALLOY 111H-5754 due to its properties such as high strength to weight ratio, ductility, toughness, and corrosion resistance, are applied in the manufacture of automotive body, offshore, and offshore oil equipment. The presence of 3% magnesium in the chemical structure of this ALLOY makes it susceptible to heat and therefore, it is not possible to perform most of the traditional machining processes on it. Water jet machining with abrasive particles (AWJM), because of the use of water and abrasive particles as cutting tools, can be a good method for machining these materials. In the present study, the effect of water jet and abrasive particle machining process parameters, including water jet pressure, traverse speed and loading coefficient on surface roughness, angle of striation, and burr formation in aluminum ALLOY 111H-5754 samples is discussed. The results showed that after traverse speed, water jet pressure and loading coefficient have the most effects on the surface quality characteristics, respectively. So, for a loading factor of 45% and a jet pressure of 300MPa, increasing the traverse speed from 200 to 300mm/min, the surface roughness value in the smooth area is about 50%, and the angle of striation of the lines in the rough area, increased by about 25%.