Abstract:
This research studied the effects of mechanical vibration in semi-solid state on primary
silicon of A390 aluminum alloy. The molten aluminum alloy was mechanically vibrated in
a stainless steel mold with six different amplitudes ranging from 17.65 to 151.38 um and
constant frequency of 200 Hz. The stainless steel mold was held in molten salt bath at
fraction of solid of 3.9, 5.0 and 7.8%. Vibration durations were set at 1, 3, or 5 min. It was
found that samples with amplitudes of 19.73 and 45.86 um had primary silicon particles
mainly within 29 to 30 um in diameter. It was believed that mechanical vibration caused the
primary silicon fragmentation. The main microstructures were eutectic structures
surrounded by aluminum dendrite. However, samples from vibration with an amplitude of
151.38 um have primary silicon mostly in diameters of 50 to 115 um. That might be a
result from the agglomerations of silicon particles.