Blended powder semisolid forming of Al7075/Al2O3 composites: Investigation of microstructure and mechanical properties

Abstract

Blended powder semisolid forming was adapted to fabricate Al7075/Al2O3 composites. The process included powders uniform distribution, mechanical alloying, and semisolid compaction. Al7075 elemental powders (20 and 63μm) were incrementally added to ethanol solution under ultrasonic mixing. Al2O3 particles with different sizes (5 and 120μm) and weight fractions (5, 10, and 20wt.%) were blended with the matrix particles using a planetary ball mill. Al7075/Al2O3 composites were then compacted at semisolid state under different pressures (40 and 80MPa). The effects of Al7075 and Al2O3 particle size, Al2O3 weight fraction, and compaction pressure on the morphology, microstructure, compaction mechanism, density, hardness, compression modulus and strength, and phase formation were measured and analyzed. The highest microstructural uniformity was achieved when large Al2O3 particles (120μm) were distributed within the small matrix particles (20μm). The density and hardness increased as the size of the reinforcing particles and the applied pressure were increased. Therefore, the composites with 20μm Al7075 and 20wt.% of 120μm Al2O3 powder compacted under 80MPa exhibited the highest improvements in relative density (98.685%), hardness (Rockwell B of 70), and compressive strength (327MPa). The results are of great value in developing high performance lightweight metal matrix composites.