Grain Refinement of Al–2%Cu Alloy Using Vibrating Mold

Vibration effects on grain refinement in aluminum alloy were investigated by mechanically vibrating metal mold during solidification. Results show that both the frequency and the half amplitude affected the grain refinement, decreasing the average grain size. We hypothesized that the average grain size can be estimated from the excitation force consolidating them. To clarify grain refinement mechanisms, experiments were conducted with different vibration starting times and different vibration periods. Moreover, a water model experiment was conducted using ammonium chloride solution. Both the equiaxed grain size and the columnar grain length were reduced by mold vibration before pouring, irrespective of the vibration period. However, when the mold was vibrated at 15 s after pouring, the columnar grain length increased. Moreover, the equiaxed grain size increased greatly. Water model experiments showed that a vibrated mold made of polycarbonate and aluminum alloy produced many crystals near the mold wall and filled the mold by vibration and induced convection. These results clarified that starting vibration before solidification is important for grain refinement.