Investigation of particle size and amount of alumina on microstructure and mechanical properties of Al matrix composite made by powder metallurgy

Abstract

Al matrix composite is well known, in which Al2O3 is the most widely used reinforcement. The aim of this study is to investigate the effect of alumina particle size and its amount on the relative density, hardness, microstructure, wear resistance, yield and compressive strength and elongation in Al–Al2O3 composites. To this end, the amount of 0–20wt.% alumina with average particle sizes 48, 12 and 3μm was used along with pure aluminum of average particle size of 30μm. Powder metallurgy is a method used in the fabrication of this composite in which the powders were mixed using a planetary ball mill. Consolidation was conducted by axial pressing at 440MPa. Sintering procedure was done at 550°C for 45min. The results indicated that as the alumina particle size is reduced, density raises at first, then, declines. Moreover, as the alumina particle size decreases, hardness, yield strength, compressive strength and elongation increase and factors such as wear resistance, microstructure grain size and distribution homogeneity in matrix decreases. For instance, as the alumina particle size gets smaller from 48 to 3μm at 10wt.% alumina, hardness rises from 50 to 70BHN, compressive strength improves from 168 to 307MPa and wear rate rises from 0.0289 to 0.0341mm3/m. On the other hand, as the amount of alumina increases, hardness and wear resistance increase and relative density and elongation is decreased. However, compressive and yield strength rise at first, then drop. For example, if the amount of alumina with 12μm particle size increases from 5 to 10wt.%, hardness increases from 47 to 62BHN and compressive strength rises from 190 to 273MPa. Nevertheless, erosion rate after 300m decreases from 0.0447 to 0.0311mm3/m.