Effects of Mechanical Vibration Factors on Size and Shape of Solid Particles in JIS AC4CH Aluminum Alloy Semi-Solid Slurry

In semi-solid forming processes for metals, it is important to make slurries with fine, round solid particles. In this study, we investigated the effects of mechanical vibration on the size and shape of solid particles. The slurry was prepared by pouring molten AC4CH aluminum alloy into a vibrating stainress container, and the vibration of the container was controlled. The solid particles in the slurry became finer and rounder with increasing acceleration amplitude at the same frequency, or with decreasing frequency at the same acceleration amplitude. However, at the same velocity amplitude and different frequency and acceleration amplitude, the solid particles formed a dendritic structure at high or low frequencies. The solid particles were the finest and roundest at a frequency of 50 Hz. The calculation results for the particle diameter and the particle roundness also showed that the solid particles became finer and rounder with increasing velocity amplitude. Additionally, the shapes of solid particles were affected by the frequency and displacement amplitude. Mechanical vibration with a frequency and displacement amplitude above certain threshold values produced fine, round solid particles. Slurry containing sufficiently fine, round particles was obtained by applying mechanical vibration at 50 Hz with an acceleration amplitude higher than 49.0 m/s(2).