New foundry process for the production of light metals in the semi-liquid, doughy state

Abstract

Subjecting a metal alloy at the time of solidification to an elevated shear rate it is possible, upon solidification, to verify a microstructure very different from the conventional ones; the effect of the shear forces induced is, indeed, to destroy the solid network of dendritic interconnections developed during solidification of the liquid. In the absence of such a structure the dendrite fragments remain separate, and tend to assume spheroidal shapes by continual mutual mechanical collisions.

The Fiat Research Centre has patented and developed a process that makes it possible to confer on the metallic alloy such globular structures based on the use of a capillary type static mixer.

The present work describes the pilot plant able to produce semiliquid metal continuously, and illustrates the operating technique for producing a casting in the doughy state.

Moreover, the microstructural characteristics of an Al-Si-Cu alloy cast in the semi-liquid state underline the inherent fluid-dynamic peculiarities possessed by such an alloy in the solidification range which allow it to be used easily in forming processes.