للكاتبين :
F. Shehata, M. Abdelhameed and A. Fathy
Department of Mechanical Design and Production Engineering,
Faculty of Engineering, Zagazig University,
ABSTRACT
A wide range of particulate metal matrix composites (PMMC) of alumina and aluminum
powders was fabricated using powder metallurgy techniques followed by extrusions at
various extrusion ratios. The alumina particles of size 37μm were used to produce PMMC
with weight fractions of 5, 10, and 15%. The mixed powders were cold pressed and sintered
at 450 °C for 6 hours in a vacuum chamber furnace. The sintered PMMCs were hot extruded
at 550 °C using various dies having extrusion ratios of 4.4, 5.5, 7.1 and 9.5. The Mechanical
and structural properties of the extruded PMMC were investigated. Results showed
significant effects of weight fractions of reinforcement and extrusion ratios on mechanical
properties. The porosity increased as weight fractions of particulate reinforcement were
increased. However, increasing extrusion ratio resulted in significant decrease in porosity
from over 2 % to 0.5 %. The higher extrusion ratios showed relatively finer and more
homogenous alumina-particle distribution within the aluminum matrix. A preferred particle
orientation to extrusion axis was also observed. The hardness, yield and ultimate tensile
strengths of the MMCs have significantly increased as weight fraction of reinforcement
particles is increased. The strengths are further increased as extrusion ratios are increased.
Increasing extrusion ratios are also accompanied by uniform distribution of fine
reinforcement particles.