抄録
Semi solid forming testing machine which has the same system as a runner-less injection machine has been made on an experimental basis. Temperature control system has been established to obtain the homogeneous solid-liquid coexisted state in its injection cylinder. Rod specimens were cast into a permanent mold by this machine in the semi solid state. The effect of solid fraction on the microstructure and the casting defect has been investigated and the results obtained as follows:
A shearing in the part of nozzle of injection cylinder is the most important to reveal thixotropic property of alloy slurry in semi solid forming process by injection machine. So it needs controlling of solid fraction to affect it. In order to decrease casting defect and hold homogeneous structure, solid fraction more over 50% is needed. But when the solid fraction increases to 60%, primary solid particles glow coarser, so the primary solid particle size control technique is required to suppress it. In the case of less than 50% of solid fraction, alloy liquid preferentially fills inside the permanent mold and alloy slurry continue to fill the mold after alloy liquid. Then large casting defect form at the boundary of both flows.
