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Metallic alloys exhibit rheological behavior similar to non-Newtonian fluids in the semi-solid temperature range. This behavior can be described using rheological models. In this study, the viscosity of semi-solid 7075 aluminum alloy was measured by using the results of load-displacement signals obtained from two different experiments: parallel plate compression and backward extrusion. The obtained data were used to determine the parameters of the Cross model in a wide range of shear rates. The effects of temperature (solid fraction) and shear rate were studied on the viscosity of the alloy. The results showed that with increasing temperature and decreasing the solid fraction the resistance to flow decreases, resulting in a reduced amount of applied forces. This reduction in applied forces results in reducing the viscosity. It was observed that the behavior of semi-solid alloy is shear thinning in which the viscosity decreases with increasing shear rate. Also, the calculated viscosity values of the four parameters Cross model were in good agreement with the obtained experimental results in a wide range of shear rates. The simulation results showed a good agreement of the presented model for predicting the rheological properties and flow behavior of the semi-solid alloy in a wide range of shear rates.

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The defectless microstructure of metal matrix composites, the uniform distribution of particles and their good properties are determined by the production parameters and the base material and reinforcement. In this study, high-energy planetary ball mill was used to fabricate Al6063-SiC composite powder. Aluminum chips were milled with different time and ball to powder weight ratio (BPR) in high energy planetary ball mill. The resulting powder was mechanically alloyed by adding different weight percentages of silicon carbide (SiC) and BPRs at different times. During the milling process under argon atmosphere, stearic acid was used as a process control agent (PCA) to prevent excessive cold welding and agglomeration of the powder. After mechanical alloying, the effect of alloying time, BPRs and weight percentage of silicon carbide, on the obtained composite powder were examined morphologically by particle size analysis (PSA), field emission scanning electron microscope (FESEM), and the fuzzy compounds by X-ray diffraction (XRD) spectroscopy. According to the X-ray diffraction pattern of the samples, grain size was calculated using the Williamson-Hall model. The results of mechanical milling and alloying process have shown that in short milling times with high BPRs composite powder with finer particle size could be achieved. Also, the presence of silicon carbide reinforcing particles accelerates the process of mechanical alloying and further reduces the particle size.