The in situ formation and dispersion behavior of TiC particles in a liquid Aluminum alloy have been investigated to develop the novel technique for fabrication of Aluminum matrix composites utilizing the spontaneous reaction among materials. Fine TiC particles were in situ formed by the reaction between SiC or Al4C3 particles and an Al-Ti alloy. The effects of processing parameters, such as the kind and size of raw carbide on the in situ formation rate of TiC have been quantitatively estimated by means of ICP analysis. The experimental results were analyzed by the in situ reaction kinetic model based on the assumption that the overall reaction rate was controlled by both the interfacial reaction and the diffusion through the generated carbide particle. At the initial stage of the TiC formation, the interfacial reaction rate is the main controlling step. However, the process is gradually controlled by the diffusion from the middle stages onwards.      

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.

The welding of materials by applying Friction Stir Welding technique is a new solid-state joining technique. The main advantage of this method compared to the traditional joining process is that it minimizes problem-related to metal resolidification as the method incorporates no melting phase. In this experimental work, the effect of friction stir welding (FSW) technique on the microstructure and mechanical properties of the cast composite matrix AA6063 reinforced with 7wt % SiC particles is studied. Friction stir welding, owing to the simultaneous effect of intense plastic deformation and frictional heat generated throughout welding, had impacts each on the reinforcement agents and the matrix alloy. FSW produced a notable reduction in the size of reinforcement agents and their homogeneous distribution in the weld region. It also induced the grain refinement due to dynamic recrystallization of the Aluminum matrix alloy in the weld area. The frictional heat generated during friction stir welding had impacts on the growth, dissolution and reprecipitation of the hardening precipitates. The microstructural changes resulted in improved mechanical properties such as UTS, elongation, and hardness of the joint. A joint efficiency of 98. 84% was observed for the welded joint. The XRD and EDX analysis of the welded area confirmed that there was no formation of any other compound due to the frictional heat produced during welding. The SEM fracture morphology of the welded joint revealed that the fracture behavior was changed from ductile to brittle following to FSW.

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.