At Vforge our expertise is semi-solid metal (SSM) processing, sometimes called thixoforming, thixoforging, or thixocasting. We process aluminum alloys in the semi-solid state which requires some extra metallurgy along with unique die and system designs. We do this because semi-solid flow offers special advantages over traditional liquid casting. For a start, semi-solid aluminum alloys are viscous (hence the “V” in our name) meaning that they do not splash and spray when entering a die but instead fill the cavity with a smooth, quiescent flow. That in itself is a tremendous asset to avoid entrapping gases inside the part. In addition, because the semi-solid material is typically more than 50% solid at the time of injection, shrinkage porosity is also eliminated. In normal casting situations, when liquid metal transitions to solid in the die or mold, it contracts 6% by volume. Without any external means to fill that deficit, so-called shrinkage cavities can occur. Our combination of semi-solid injection and high, final pressure provide fully dense, pressure tight, and heat-treatable parts.
But it gets better. Because semi-solid metal transfers far less heat to the die than molten aluminum which therefore last longer providing additional benefits to our customers by reducing ongoing tooling replacement costs.