Gears are one of the most critical components in power transmission system of an automobile and also many rotating machinery. Many studies have been conducted on optimum gear design. The main objective is to design different aluminium METAL MATRIX COMPOSITE spur gears before and after optimization. Aluminium METAL MATRIX material COMPOSITEs are preferred mostly due to their low density. Also the high specific mechanical properties make these alloys one of the most interesting material alternatives for the manufacture of lightweight parts for many types of vehicles. With wear resistance and strength equal to cast iron, 67% lower density and three times thermal conductivity, aluminium MMC alloys are ideal materials for the manufacture of lightweight automotive and other commercial parts. In the present work materials considered are Al 6061-T6, Al 6106-T6, Al 7075-T651, and Al 7050-T7451. Finite Element Analysis is performed on different spur gears using above materials and the results will be compared.

Effects of temperature on properties and behavior of a 20 vol % particulate SiC reinforced 6061 aluminum alloy and 6061 unreinforced Al alloy were investigated. Yield strength and elongation to failure were measured as a function of test temperatures up to 180^oC. In addition, the effects of holding time at 180^ oC on tensile properties and fracture mechanisms of the materials at this temperature were studied. The behaviors of the materials were characterized by using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS), X-ray diffraction (XRD), atomic absorption (AA), hardness measurement and image analyzing (IA). The results show that an increase in temperature leads to a decrease in the yield strength and increase in the elongation to failure of the materials. On the other hand, while increasing holding time at 180^oC produces an increase in the elongation to failure of the unreinforced alloy, it reduces the elongation to failure of the COMPOSITE. It was also observed that reduction in yield strength with increasing holding time at 180^oC was faster for the COMPOSITE material compared to the unreinforced alloy. The results from SEM, XRD, EDS, IA and hardness tests indicated that some chemical reactions had taken place at the interface between the reinforcement and the MATRIX alloy during holding the specimens at elevated temperature. Therefore, different trend in elongation to failure of the unreinforced alloy and the COMPOSITE material with holding time at elevated temperature could be attributed to development of chemical reactions between the reinforcement and the MATRIX alloy at the interface.

For the past decades researchers are showing immense interest to investigate the natural advantage of preparation of COMPOSITEs from minerals such as bauxite particles, and proved their effectiveness as cost effective reinforcing agents in fabrication of high performance COMPOSITEs. This study, is a new attempt in using the Iraqi natural bauxite powder with different proportions (2, 4 and 6 wt%) in preparation of aluminum METAL MATRIX COMPOSITEs (AMMCs) using stir casting and Mg additives. In experimental work, the bauxite stones were crashed and milled, then the powder was fired at 1400 ○C. The powders were characterized using particle size, XRD and XRF analysis. The AMMCs casts were machined, polished, preheated, and their properties were characterized using hardness measurements, microstructural observations, and calculation of their Young's modulus, Poisson’s ratio and fracture toughness. Also, their fracture toughness were evaluated by means of crack mouth opening displacement (CMOD) measurements from extensometer recordings. The results proved the successful production of AMMCs with improved fracture toughness, hardness and elastic modulus properties using Mg and Iraqi fired bauxite added at 2 and 4 wt% by stir casting. Moreover, results from CMOD measurements showed the effect of addition bauxite particles at 2 and 4 wt% in increasing "maximum load at failure" and "critical CMOD at critical load" of the MATRIX materials to about " 25 and 44%" , and " 32 and 47%", respectively. Also, at these ratios, the calculated fracture toughness of the MATRIX materials by means of KIC, and young modulus showed improvement at about “22 and 69%”, and “8 and 12%”, respectively. Addition of bauxite at 6% could not give the required improvement in the fracture toughness despite its effects in recording the highest improvements in hardness (57%)   and elastic modulus (22%) due to the brittle behavior of AMMCs at this ratio.

in this study, in situ surface COMPOSITE based on Mg-Cu system produced on AZ91C alloy by friction stir processing. Microstructural studing in the 6 passes friction stirred zone, revealed the presence of Mg2Cu interMETALlic phase in AZ91/Cu nanoCOMPOSITE. after T6 heat treatment, microhardness value within the stirred zone increased due to increasing volume fraction of hard interMETALlics and formation of Mg2Cu2 phase in the COMPOSITE. Wear surface and debris observation indicated that abrasion and delamination wear mechanisms occurred in AZ91C alloy. The results of EDS and microhardness test on AZ91/Cu sample revealed that hardness and durability of oxide film on wear surface was more than that of the base alloy, which led to decrease wear mass loss of the COMPOSITE in comparison with base METAL. the results of wear test revealed that T6 heat treatment weakened wear properties, compared with not heat treated COMPOSITE. COMPOSITE samples Wear rate increased because of microcrack formation during heat treatment which caused delamination occurrence in this wear sample.

In the present study a Ti-B2 containing METAL MATRIX COMPOSITE has been made by mixing of two molten master alloys, Al-8%Ti and Al- 4%B. The weight ratio of Ti:B was selected in an appropriate portion to ensure the formation of TiB2 particles in aluminum MATRIX. The Al-8%Ti and Al-4%B master alloys were made by K2TiF6 and KBF4 salts in an induction furnace. The mechanism of formation of the TiB2 particles was studied by an optical microscope equipped with a Hot Stage, providing direct observation of phase transformation by recording real images. The study of phase transformation of solidified specimen microstructures was made by a scanning electron microscope coupled with EDAX analyzer. The results obtained from Hot Stage studies indicated that the boron atoms migrate easily towards TiAl3 particles to produce very fine TiB2 particles on the interface of TiAl3 particles and MATRIX alloy. Small atomic radius of boron and the ease of its diffusion may cause the readily access of boron on the interface and also formation of agglomerated TiB2 particles, as a result of exothermic reaction of TiB2 formation. The micro structural studies of the real-time observation showed that due to the high mobility of TiB2 particles and their easily separation from TiAl3 particles, the growth rate of these particles is high and penetration of boron into the TiAl3 particles leads to the replacement of agglomerated TiB2 particles (in a ring shaped) with large TiAl3 particles.

The effect of SPEX mechanichal milling on a mixture of Al-SiC COMPOSITEs has been investigated. Results of XRD, SEM and cumulative size distribution analysis show that the size of crystallites is decreased as milling time increases to 12 hours, while lattice strains are increased.Meanwhile the crytallite size increases with increasing milling time between 12 and 24 hours, but the lattice strains decreas. In addition, average particle size of the COMPOSITE decreses at initial 6 hours but increases for longer milling times. SEM and TEM micrographs of the productions indicate homogeneous distribution of 50 nm size SiC particles into Al MATRIX, where the homogeneity increases with increasing milling time.  

Repairing cracked parts using patches is a common method to restore mechanical properties and tensile strength. The efficiency of such patches can be achieved by obtaining the maximum amount of force borne by the repaired part and comparing it with the non-repaired part. The purpose of this study is to investigate the diffusion method used in the repair of cracked aluminum parts and to evaluate the patches and fibers used. In this study, the diffusion method is used to connect the aluminum patch to repair the central crack in the aluminum thin sheet. Examination of microstructures showed that using the diffusion method, parts can be welded together and a suitable part can be obtained without the use of glue. The process of repairing cracked parts made of aluminum or its alloys in this study involves the use of three types of patches and different fibers and different conditions, and finally pressing the patch and the piece together under heat for a certain period of time. The repaired parts are subjected to quasi-static tensile loading and the maximum amount of force borne by the part is obtained in different states.

Al7075 alloy reinforced with h-Boron Nitrate (BN) COMPOSITEs were processed by stir casting technique. The produced COMPOSITE was subjected to microstructural studies using OLYMPUS-BX51M, tensile, hardness, density and wear tests. Tensile strength and hardness were found to increase by 12. 8% and 20% respectively due to increased dislocation density with the addition of reinforcement. Microstructure showed grain refinement with reinforcement addition and reinforcement acts as nucleating sites with an approximately uniform distribution of reinforcements. Wear test was conducted with different loads 10, 20 and 30N for a sliding distance of 1500 m. Wear mass loss of COMPOSITEs showed improved wear resistance with variation in reinforcements. Worn surfaces were examined using SEM, which showed the presence of delamination, plough and debris on the surface. Due to the addition of low-density h-BN, the density of COMPOSITEs decreases with increase in reinforcement content.