Mechanochemically Prepared and Spark Plasma Sintered Aluminum Matrix Composite with Ceramic and Intermetallic Reinforcement

Preparation of aluminium matrix composites reinforced by fine niobium boride particles was investigated while exploiting the advantages of mechano-chemical processing and spark plasma sintering. For this purpose, a mixture of aluminium, niobium and boron (III) oxide powders were subjected to high energy ball milling. Subsequently, spark plasma sintering was applied. The microstructures of the powder mixture before and after sintering were characterized via X-ray diffraction and scanning electron microscopic observation. Nanoindentation was also employed to characterize the composite performance. X-ray diffraction analysis showed formation of niobium boride particles after mechano-chemical processing. The results indicated that the volume fraction of niobium boride particles was significantly increased and intermetallic Al 3 Nb particles have been detected after the spark plasma sintering. The instrumented indentation revealed improvement in hardness by 2.9 GPa as well as in the modulus of elasticity by 98 GPa; the final values of 5.7 GPa and 135 GPa respectively being higher than those of comparable aluminium matrix composites.