THE CAST Cooperative Research Centre (CAST CRC) has discovered molten metals can behave like wet sand when they enter a zone between solid and liquid states.
According to the researchers, as molten metal alloys cool, they enter a “twilight zone” where they switch from liquid to solid.
This state is the origin of many problems that plague metal castings. By learning more about the metals at this stage, manufacturers might be able to produce better quality metal parts more efficiently and cheaper.
This zone happens for metal alloys when they cool from a liquid and start forming numerous solid crystals. The alloys become a mixture of solidifying grains surrounded by liquid – thus the wet sand analogy.
Wet sand dries up when weight is exerted on it. The sand grains are forced apart, increasing the space between them. The liquid surrounding the grain is drawn into the expanding spaces, resulting in the sand drying.
The new research shows metal crystals can be similarly pushed apart by applying pressure, causing alloys to expand as they deform. This could have implications for metal manufacturing processes like high pressure die-casting, often used to form alloys into car parts.
Scientists hope to develop processes or technologies to enable manufacturers to control deformation in the solid-liquid stage, making metal components with fewer imperfections and better properties.

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