Synthesis and characterization of aluminium–alumina micro- and nano-composites by spark plasma sintering

• The Al–Al2O3 micro- and nano-composites fabricated by spark plasma sintering.
• Better matrix-reinforcement integrity in nanocomposites than microcomposites.
• Spark plasma sintering method results in higher density and hardness values.
• High density and hardness values of nanocomposites than microcomposites.
• High dislocation density in spark plasma sintered Al–Al2O3 composites.

In the present study, an emphasis has been laid on evaluation of the microstructural morphologies and their implications on mechanical performance of the composites by varying the reinforcement particle size. Nanocomposites of 0.5, 1, 3, 5, 7 volume % alumina (average size < 50 nm) and microcomposites of 1, 5, 20 volume % of alumina (average size ~ 10 μm) reinforced in aluminium matrix were fabricated by spark plasma sintering technique at a temperature of 773 K and pressure of 50 MPa. These micro- and nano-composites have been characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy followed by density, microhardness and nanoindentation hardness measurements. The alumina nanoparticles revealed appreciable physical intimacy with the aluminium matrix than that of alumina microparticles. The highest nanohardness recorded 0.85 GPa and 99% densification for 7 and 1 vol.% Al–Al2O3 nancomposites respectively. Spark plasma sintering imparts enhanced densification and matrix-reinforcement proximity which have been corroborated with the experimental results.

The evolution of microstructure by varying the particle size of reinforcement in the matrix employing spark plasma sintering has been demonstrated here in Al–Al2O3 system. An emphasis has been laid on varying the reinforcement particle size and evaluating the microstructural morphologies and their implications on mechanical performance of the composites. Nanocomposites of 0.5, 1, 3, 5, 7 volume % alumina (average size < 50 nm) reinforced in aluminium matrix were fabricated by powder metallurgy route using spark plasma sintering technique technique at a temperature of 773 K and pressure of 50 MPa. Another set of specimens having composition 1, 5, 20 vol.% of alumina (average size ~ 10 μm) had been fabricated to compare the physical as well as mechanical attributes of the microcomposite as well as the nanocomposites. These micro- and nano-composites have been characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy followed by density, microhardness and nanoindentation measurements. The alumina nanoparticles revealed an interface showing appreciable physical intimacy with the aluminium matrix compared to that of the alumina microparticles. The interfacial integrity in case of nanocomposites is better than in the microcomposite which has been studied using microscopic techniques. Spark plasma sintering imparts enhanced densification as well as matrix-reinforcement proximity which has been corroborated with the experimental results.Figure optionsDownload as PowerPoint slide