Although the solubility of oxygen in molten aluminum alloys is said to be negligible, the fresh surface of the melt oxidizes quickly in the air and an oxide film is formed on the melt surface. Oxide-metal-oxide sandwich technique is a method for the study of short-time surface oxide films. In this research, air was blown at 0.5 atmosphere into the melts of Al-1Mg and Al-6Mg alloys by means of a compressor in order to form air bubbles within the melts. The sandwiches of oxide-metal-oxide were formed at locations where these bubbles reach each other. Some of the characteristics of these films inside the bubbles were evaluated using the scanning electron microscope. In Al-1Mg alloy, the formation of crystalline aluminum oxide as well as the granules of magnesium oxide at the same time was confirmed whereas the magnesium oxide in the form of layer and granule was detected for the case of Al-6Mg alloy.

In this research work nano porous silicon layers with different porosity were prepared by using electrochemical etching. Surface morphology and size of pores were investigated by scanning electron microscopy (SEM). TiO2 thin films with EBPVD method have been deposited on the surface of PSi layers. The influence of anodization conditions such as anodization time interval and current density on electrical properties and surface morphology of sandwich devices were carried out using I-V measurements .The results showed that, electrical properties were influenced by changes of current density and anodization time interval. We also investigated the AC electrical conductivity of Al/TiO2/PSi/Al sandwich devices over the range of frequency 102 to 105 Hz and temperature range 300 to 378 K. It is known that, over the range of frequency<103Hz the band theory and over the range of frequency>103Hz hopping mechanism is applicable in explaining the conductivity of TiO2/PSi thin films nano structures with aluminum electrodes.

In the current study the microstructure and mechanical properties of Al-2Ni-xMn alloys was investigated as a substitute for Al-4Ni alloys. To this end, different melts containing 2 wt. % Ni and 1, 2, and 4 wt. % Mn were solidified at two cooling rates of 3.5 and 10.4 C/s. According to the results, under the low solidification rate, the tensile strength, fracture strain, and toughness of Al-2Ni-1Mn alloy are lower than those of Al-4Ni alloy by 26, 115, and 137%, respectively. However, further Mn addition impaired the tensile properties. Increasing the solidification cooling rate decreases the size and improves the distribution of Ni(Mn)-rich compounds and porosities within the microstructure and reduces the sizes of secondary dendrite arm spacing and grains. This substantially improved the mechanical properties of Mn-rich alloys. For instance, compared to Al-4Ni alloy solidified at 3.5 C/s, the tensile strength, fracture strain, and toughness of copper mold cast Al-2Ni-1Mn alloy increased by 50, 200, and 330%, respectively.

Incremental sheet metal forming is one of methods more innovation in science and industrial zone. The purpose of this research is the study of influence of factors such as tool diameter, step down, rotation speed and feed rate on metallurgical properties of explosive-welded Al/Cu/Al multilayer. In order to this purpose, a sample of explosive-welded Al/Cu/Al multilayer was produced. Then, a statistical model (RSM) was used for the experimental plan (with these variables) to determine the runs of experiment (or selected points). Next, forces and times values of sheet metal forming were measured. The experimental results showed that force and time forming of Al/Cu/Al multilayer is highly sensitive to factors like step down and feed rate. Also the most effective coefficient on the incremental forming is belonged to step down factor that showed it is very important in machining parameters. Finally, by using coefficient estimates of (RSM) model, relation between input variables and response was obtained. Finally, this model was predicted the optimum design points of machining parameters.

Optimization of Stir Friction Welding parameters such as linear and rotational speed of the tool can be effective to a large extent in improving welding properties. In this research, welding of two sheets of Aluminum of Al-7075 and Al-6061 were validated based on theoretical relations and numerical simulation. The simulation of the contact characteristics of the workpieces with the tool was done using the contact algorithms available in the Ansys software. From the FEM, rotational and linear speed and diameter of the tool were selected as design variables, and multi object optimization was carried out with genetic algorithm and RSM to reach the lowest tool temperature and residual stress. The parametric analysis of FSW of the threaded and non-threaded tool pins showed that the generated heat has proportional and inverse relation with rotation and linear speed of tool respectively. Tool with a diameter of 20 mm showed minimum residual stress in the workpiece. By increasing welding speed, the temperature curves become more compact and the effect of thread on heat generation was more evident in all cases at lower heat input.

A rolled AA3003-H14 aluminum alloy sheet and Titanium metal powders were used to fabricate Al-surface composites reinforced by in-situ formed Al3Ti aluminide nanoparticles while applying friction stir processing (FSP). The titanium powder of particle sizes smaller than 45 microns was used as reinforcement. Tensile strength and the hardness of the surface composites were determined after applying 6 passes FSP. Its phase analysis was done by using an X-ray diffraction and the microstructural examinations were performed using an optical microscope and scanning electron microscopy. Microstructural examinations revealed that the large size and elongated grains of the base metal have transformed into a more homogeneous, equiaxed and smaller ones after applying FSP. It was also noticed that the reaction between the titanium powders and the aluminum matrix led to the formation of Al3Ti aluminide at the interface between the two elements. This aluminide formation was in the form of a spherical shell around the aluminum, wherein the later stage of processing fragmented into smaller particles and distributed throughout the matrix. Results showed that tensile strength and the hardness of the base metal were increased by about 30% after applying 6 passes FSP.

In this research work, the possibility of semi industrial production of AI-TiB2 and AI-ZrB2 composites, using reactive slag in a flanu furnace have been investigated. For this purpose, commercial pure aluminum and powder mixturt of TiO2 (ZrO-2 , KBF4 and Na3AlF6 were used. The results showed that using a proper ratio of slag forming materials as well as proper amounts of the above-mentioned compounds make it possible to produce good quality Al- TiB2 and Ai-ZrB2 compounds employing the conventional melting equipment such as aflame furnace.

In this research casted Aluminum alloy A356 and Al2O3 powder were used as matrix and reinforcement, respectively. 5wt. % of Al2O3 with Al powder in the ratio of Al/Al2O3=1 for increasing the wettability were milled and injected to melt. Three different argon flow gas rate (2.5, 5, 10 liter/min) were selected for injection Al2O3(p) within molten Al and investigated the effects of that on microstructure and mechanical properties. Results showed, with increasing powder gas flow rate from 2.5 to 5 liter/min, mechanical properties such as hardness and compression strength are enhanced from 62.28 HB and 230.2 MPa to 78.7 HB and 539.1 MPa, respectively. While wear test represents decreasing of around 26 percent in coefficient of friction. But, with further enhancement in gas flow rate to 10 liter/min due to porosity increasing and agglomeration of Al2O3 particles, hardness and compression strength in comparison of composite with 5 liter/min flow rate reduced 21 and 37 percent, respectively. In this way, coefficient of moderate friction increased from 0.42 in composite with 5 liter/min flow rate to 0.56 in metal matrix composite with 10 liter/min flow rate.