Improving earthquake resistance with a single crystal

A new heating method for certain metals could lead to improved earthquake-resistant construction materials.

Tohoku University researchers and colleagues have found an economical way to improve the properties of some 'shape memory' metals, known for their ability to return to their original shape after being deformed. The method could make way for the mass production of these improved metals for a variety of applications, including earthquake-resistant construction materials.

Most metals are made of a large number of crystals but, in some cases, their properties improve when they are formed of a single crystal. However, single-crystal metals are expensive to produce.

Researchers have developed a cheaper production method that takes advantage of a phenomenon known as 'abnormal grain growth.' By using this method, a metal's multiple 'grains', or crystals, grow irregularly, some at the expense of others, when it is exposed to heat.

The team's technique involves several cycles of heating and cooling that results in a single-crystal metal bar 70 centimetres in length and 15 millimetres in diameter. This is very large compared to the sizes of current shape memory alloy bars, making it suitable for building and civil engineering applications, says Toshihiro Omori, the lead researcher in the study.

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