EFFECT OF SOME MANFACTURING PARAMETERS ON MECHANICAL PROPRTIES OF EXTRUDED Al-ALUMINA COMPOSITES

Department of Mechanical Design and Production Engineering,

Faculty of Engineering, Zagazig University,

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.