الفهرس 
Abstract
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Abstract
Aluminum Metal matrix nanocomposites Al-Al2O3, and Al-Al2O3-ZrO2 systems were synthesized by mechanical alloying (MA) (solid state powder processing technique) to obtain advanced engineering materials with improved properties. High energy milling of powders: starting from the mieron size: is carried out at a ball-to- powder ratio of 10:1. In Al-Al2O3 system, three various sets of experiments are prepared with rotation speeds of 200, 300, and 400 rpm. For the three experiments sets. Al-20wt. %Al2O3 is selected to investigate the effect of milling speed and milling time on the mechanical behavior of the composite. Al-Al2O3-ZrO2 system is fabrieated to study the influence of using weight fraction of both the alumina and zirconia partieles, as reinforcement for aluminum matrix, on the properties of the formed nanocomposite material. Al-10wt, % Al2O3-10wt. %ZrO2 was selected as the weight fraction of the hybrid nanocomposite.
A homogenous distribution of the reinforcements in the Al matrix was obtained after milling the mixed powders for a period of 60, 45 and 30 h at 200, 300, 400 rpm milling speed respectively for Al-Al2O3 system and for a period of 45 h at 300 rpm for Al-Al2O3-ZrO2 system. The powders were consolidated by cold pressing under 600 MPa pressure at room temperature followed by sintering at 600 C for 45 min under N2 gas atmosphere to a fully dense condition. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and transmission Electron Microscopes (TEM) techniques were used for the crystal structure and microstructural characterization of the powders at different stages of milling.
X-rauy patterns were analyzed by using the Williamson-Hall treatment to determine the crystallite size and the strain. X-ray analysis indicates that crystallite size decreases with milling time and, at the same time, the lattice strain increases to a steady state value. Microhardness measurements and compression tests were performed to characterize the consolidated composite materials. Microhardness results gives 78HV for Al-Al2O3 at 200rpm, 83HV at 300rpm and 80HV at 400rpm.