Going against the grain

Close-up ... metal crystals under an optical microscope

Life in the laboratory is a stroll along the beach for two UQ researchers, after discovering that metals bear exciting similarities to granular materials such as sand. Christopher Gourlay and Professor Arne Dahle, from the CAST Cooperative Research Centre, made the discovery when deforming metals as they were solidifying, publishing their findings in the journal, Nature.

The authors explain that we are all familiar with wet sand drying up around our feet when we walk on the beach. This happens because our weight forces the sand grains to rearrange, opening up spaces into which the surrounding water flows – a phenomenon known as “dilatancy”, first described in 1885.

Mr Gourlay and Professor Dahle have proven for the first time that metallic alloys can expand in the same way when cooled from the liquid state – the process used to make everyday items such as steering wheels and mobile phone covers. Mr Gourlay said the findings were an important step towards understanding how metals deformed during industrial-casting processes.

Professor Dahle said the findings opened up exciting links between alloy solidification and research areas as diverse as volcano and earthquake science, soil mechanics and the processing of cereal crops.

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