Effect of volume fraction and particle size of alumina reinforcement on compaction and densification behavior of Al–Al2O3 nanocomposites

Advance on Al2O3 Particulates Reinforced Aluminum Metal Matrix Composites (Al-MMCs) Manufactured by the Power Metallurgy Techniques- Microstructure and Properties

“…Raising the particle size of Al 2 O 3 from 3 µm to 12 µm led to the relative density increasing from 96.5% to 96.8% [24]. In the sample with 7 vol% nano-alumina powders, the maximum relative density of 89.5% could be obtained, which was far lower than that of sample with submicron Al 2 O 3 particle, of which the maximum relative density of 94.1% could be achieved [16]. However, some controversial results were also observed.…”

“…The grain coarsening could be compensated by the pin effect of the finer alumina. In the sample reinforced by 7 vol% nano-alumina, the grain size remained between 50 nm and 150 nm approximately [16]. Even heated for up to 480 min at 640°C, the overall neck growth and particle coarsening were hindered, although several neck junctions could be observed in the microstructure.…”

“…The higher volume fraction of alumina phase resulted in smaller particle size of composite powders. And then when sintered, the finer grains of the composites could be obtained [16].…”

“…The addition of nano-alumina powder caused a considerable reduction in the relative density from 96.8% to 89.0%. It was suggested that a higher volume fraction resulted in a smaller interparticle spacing, which caused a negative effect on the sintering for the presence of the rigid particles at surfaces, and accordingly brought the decreasing of relative density [16]. Rahimian et al [29,35] concluded that it was caused by reduction in compressibility of the powder and the inhibiting effect of alumina in the rearrangement of the particles during sintering, due to a great difference in the melting points of the matrix and the reinforcement.…”

“…First, Al 2 O 3 particles are characterized by high stability, inert and thermal stability, and low-cost effectiveness compared to Al 2 O 3 fibers, making it one of the most popular in the strengthening particles, such as SiC, AlN, BN, and so on [2,[13][14][15]. Second, the PM methods has been outstandingly developed recently and become one of the most effective and economical methods for manufacturing Al-MMCs, which can diminish the segregation and agglomeration of the reinforcement particles, as well as harmful reactions at the interface [16][17][18]. Third, the PM techniques are believed to be a more suitable process than other methods for the production of Al-MMCs [19][20][21].…”