In this study, mechanically milled (MM) Al-24TiO2-20B2O3 powder in molten Al7075 matrix was used in order to fabricate in-situ TiB2 and Al2O3 reinforcements in Al7075 matrix. Differential thermal analysis (DTA) examination was adopted to find reaction temperature between milled Al, TiO2, and B2O3 powders. X-Ray Diffraction (XRD) patterns showed the existence of TiB2 and Al2O3 peaks (750 °, C at Ar atmosphere) in MM powder. Scanning Electron Microscopy (SEM) results revealed the uniform distribution of TiO2 and B2O3 particles in the aluminum matrix. 6 wt. % MM powder was added to molten Al7075 at 750 °, C. The molten Al7075/TiB2-Al2O3 composite was poured in copper mold. The Stir casted composites were hot extruded at 465 °, C with extrusion ratio of 6: 1 and ram speed of 5 mm/s. The microstructures (optical microscopy and TEM) and mechanical properties (hardness and tensile testing) of samples were evaluated. TEM results showed that in-situ TiB2 nanoparticles were formed. The tensile strength of extruded Al7075/TiB2-Al2O3 composite was reached the value of 496 MPa. This result was around four times greater than that of the as cast Al7075 alloy.

This study investigated the effect of adding boron carbide microparticles (B4C) and titanium diboride nanoparticles (TiB2) on the microstructure, tensile strength, and hardness of A356 aluminum composite. In so doing, 2.5, 5, and 7.5 vol.% B4C reinforcements and 2.5 vol.% TiB2 reinforcement were added to the field by Stir casting at 1000 °C using in situ process. The TiB2 nanoparticles were processed in situ by cryolite precursors (Na3AlF6), titanium oxide (TiO2), and potassium tetrafluoroborate (KBF4) in aluminum melt, and B4C microparticles were added directly into the melt. X-ray diffraction (XRD), optical microscope (OM), and scanning electron microscope (SEM) were used to investigate the microstructure and failure mechanism of the samples. Also, hardness and tensile tests were carried out to test mechanical properties. The results showed that addition of B4C first decreased and then increased the ultimate tensile strength compared to the sample without reinforcement. Moreover, the highest value of tensile strength was for the sample containing 2.5 vol.% of B4C and 2.5 vol.% TiB2, which showed a 235% improvement compared to the sample without an amplifier. However, the tensile strength of the sample containing 2.5 vol.% of B4C was reduced by 35% compared to the sample without reinforcement. The results of the hardness test showed a drop in properties of the samples containing 2.5% of B4C reinforcement. the highest value of tensile strength was for the sample containing 2.5 vol.% of B4C and 2.5 vol.% TiB2, which showed a 33% improvement compared to the sample without reinforcement.

The Purpose of this study is fabrication aluminum matrix composites reinforced with TiB2 in situ ceramic particles by the Stir casting process. So, produce composites with 2%, 4% and 6 wt% and contrast with AA5083 alloy of reinforcing particles without. In this study, in order to impurities and surface contamination cleanse and also water molecules contained in the powders of TiO2 and B2O3, preheating operation performed on them. Then milling operation done with speed 750 Rpm for 15 hours, in order to mechanical activation and prevent performed of adverse reactions between the powders in during the casting process. After preparing the powders, they are stoichiometric determined ratio to achieve values of 2%, 4% and 6wt% TiB2 phase were added to the AA5083 alloy molten and after Stirring for 15 minutes with speed 350 Rpm, the casting was performed. At the end of in order to properties improve of casting specimens from used hot extrusion process. Then, using phase analysis (XRD), microstructure analysis (OM and SEM) and tensile, hardness and density tests, production or non-production, distribution of reinforcing particles and mechanical properties investigated of samples. The ultimate goal of this research is, using a combined method to problems solve of cast aluminum matrix composites and improving their properties. The results showed an improvement in mechanical properties of samples with increasing reinforcing particles up to 4wt% after completion treatment. As the highest tensile strength and hardness obtained at cast and extruded sample (at temperature of 330 ° C) AA5083/4% TiB2.

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, A356 aluminum alloy matrix composites reinforced with different weight percentages of SiC nano- and microparticles respectively with 50 nm and 5 mm average particle sizes were fabricated by Stir casting method. Due to the effect of T6 heat treatment on the strength and hardness of A356 alloy, the obtained composites were subjected to the T6 heat treatment. The mechanical properties such as hardness and compressive properties of the composites were investigated. Microstructures of the samples were also investigated by an optical microscope (OM), scanning electron microscope (SEM) and field emission scanning electron microscope (FESEM). Microstructural investigation indicated that T6 heat treatment led to the change of eutectic silicon morphology and formation of the Mg2Si precipitates during age hardening stage, leading to increased hardness and compressive strength. The results showed that an increase in wt.% of nanoparticles leading to increased hardness and compressive strength. The results of microstructural investigation showed the relatively uniform distribution of reinforcement particles. Also, the strength and hardness of the composites reinforced with nanoparticles were greater than those of the composite reinforced with microparticles, even with higher weight percent of reinforcement particles. Hardness and compressive strength at 35% strain for the composite reinforced with 1.5 wt.% nanoparticles were respectively obtained 62 HBN and 252MPa, which are improved compared to the base alloy.

In this study, particulate nanocomposites with A356 aluminum alloy as a matrix reinforced with 1 and 1.5 wt.% SiC nanoparticles with 50 nm average grain size were fabricated by Stir casting method and then the obtained composites were subjected to T6 heat treatment. The mechanical properties such as Hardness Test and Tensile Test of composites samples were investigated. Microstructures of the samples were also investigated by using optical microscope (OM) and scanning electron microscope (SEM). The results show that T6 heat treated nanocomposites have significantly higher hardness and tensile strength compared to the nanocomposites without heat treatment. The enhancement in the mechanical properties is due to the formation of Mg2Si phase and globular silicon particles. Also, increasing of concentration of SiC nanoparticles led to improvement in hardness and tensile strength, so that the highest tensile strength and hardness was obtained for the 1.5 wt.% SiC nanocomposite. Tensile strength and hardness of 1.5 wt% SiC nanocomposites before and after T6 heat treatment achieved 177 MPa and 236 MPa and 80 HBN and 123 HBN, respectively. Fracture surfaces studied using SEM show that failure of all samples is brittle fracture.

In the present investigation, a A356 aluminum alloy based composite has been produced by the addition of boron nitride powder with three different conditions including raw powders, coated powder using Ni-P electroless bath and coated aluminum particles with Ni-P/ BN(h) surface composite. Moreover, parameters such as impeller shape and rotation speed have been examined in order to obtain optimized conditions. The results based on scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) showed that the pre-treatment has a main role in deposition of Ni-P on the surface of BN (h) powders. Also, it was obtained that optimum pretreatment consisting of oxidation in 200oC for 1 hr, sensitization in 10g/l SnCl2+30ml/l HCl solution for 15 minutes and then activation in 0.25 g/l PdCl2+30ml/l HCl solution. Moreover, results showed that the optimum value of added powders was 6% after coating on aluminum particles using the Ni-P electroless bath. Furthermore, the agitator of four-blade type with a radial flow was a good choice for the manufacture of aluminum/boron nitride composite. Also, it was shown that tensile strength of composite materials is not proportional with hardness, so that the tensile strength can decrease while hardness increases.

The effect of pouring temperature while preparing Al SiC metal matrix composites, with additional benefits of magnesium and copper through Stir casting technique were investigated. The composites were fabricated by mixing 12 wt% of SiC reinforcements, 4 wt% magnesium and 2 wt% copper into 6061 aluminium alloy melt at different pouring temperatures (630 ºC, 670 ºC and 710ºC). The addition of magnesium will enhance the wettability of the SiC particles with Al matrix and subsequently increase its interface bonding strength. The inclusion of copper has considerable improvement in strength and hardness of the composite. The microstructure and mechanical properties (tensile strength and hardness) of the Al MMC are evaluated with the corresponding processing parameter, specifically pouring temperature of the cast composite. The metallurgical characterization utilizing optical and scanning electron microscope were observed for the prepared composites. The coarse microstructure and homogenous distribution of alloying elements along with SiC particles were appeared within dendrite structures of the Al SiC composites. The SiC particles has effectively distributed and produced better bonding strength in composites prepared with 670ºC pouring temperature. Higher tensile strength and maximum hardness have occurred in composite at pouring temperature of 670ºC as compared to other composites. The mechanical properties were lower in composites prepared using lesser pouring temperature (630ºC) and significantly decreased for higher pouring temperature (710ºC) of the composites.

In this research, the multi-pass friction Stir processing on AZ91 alloy has been simulated with the three-dimensional numerical modeling based on the ABAQUS/ Explicit. This simulation involves the Johnson-Cook models for defining the material behavior during this intense plastic deformation and investing the fracture criterion. Friction Stir processing is a complex process that includes several issues such as high strain rate deformation, microstructure evolution, the asymmetric flow of material, and heat. Therefore, the modeling of this process is challenging. This model simulates the tool plunging and Stirring phases in the two-pass process. In this paper, to prevent too much damage in the elements during processing, the Arbitrary Lagrangian-Eulerian technique for automatically remeshing of distorted elements has been used. This work shows that the numerical modeling can be an efficient method to study the effect of process parameters on the thermal evolution and the stress distribution. The thermal model was calibrated using the experimental results from the previous works. This model can predict the transient temperature distribution and residual stress field during FSP on AZ91. The results show that the maximum temperature in the advancing side is more than that in the retreating side. In addition, numerical results show that at the end-position of the process, the tool during the lift-up leaves the keyhole region in a compressive stress state.