| 摘要 |
<p>A metal flow system is provided for use in pressure casting of an alloy, using a pressure casting machine having a source of supply of molten alloy. The system includes a mould or die tool component which defines at least part of a flow path into which molten alloy is receivable from the source of supply and along which alloy is able to flow for injection into a die cavity defined by a mould or die. The mould or die tool component defines, as part of the flow path, a controlled expansion port (a CEP) which, from an inlet end to an outlet end of the CEP, increases in cross-sectional area whereby the state of alloy in its flow through the CEP is able to be modified from a molten state to achieve a semi-solid state possessing thixotropic properties and to enable the alloy in that state to flow into the die cavity. The CEP has a form such that, with solidification of alloy in the die cavity and back along the flow path into the CEP, to provide a resultant casting having a microstructure characterised by fine, degenerate dendrite, or spheroidal or rounded, primary particles in a matrix of secondary phase, alloy solidified in the CEP has microstructure characterised by striations or bands extending transversely with respect to the alloy flow therethrough, with the bands resulting from alloy element separation, and with alternate bands relatively richer in respective elements and respectively in primary and secondary phases.</p> |
