BigPatents India

This invention relates to a metal flow system for use in pressure casting of magnesium alloy in a semi-solid or thixotropic stage, using a pressure casting meachine having a supply of the alloy in a molten state and a mould or die which defines a die cavity, wherein the system has a die or mould tool means which defines at least one runner of the system into which molten magnesium alloy is able to be received for injection of alloy into the die cavity, the flow system is of a form providing for control of metal flow velocities therein whereby substantially all of the metal flowing throughout the die cavity is in a semi-solid state, and said form results from the system including at least one controlled expansion region in which region int he metal flow is able to spread laterally, with respect to its direction of injection, with a resultant reduction in its flow velocity relative to its velocity in teh runner, whereby the state of the alloy is changed from said molten state to said semi-solid state. This invention also relates to a process for producing a casting of a magnesium alloy.