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1.1.2 Short description

Nanostructured metals and alloys are defined as solids having structural features in the range of 1-100 nm in at least one dimension. In an ordinary metal the grain size is typically in the range of a few to hundreds micrometers.

Bulk forms of nanostructured metals and alloys exhibit improved mechanical properties (e.g. extraordinarily high strength) and have been studied extensively for several decades. According to Lux Research, the total market of nanostructured metals in 2010 will be around 200$ million (assessed in 2007).

The most relevant nanostructured metals to be applied for transport applications are aluminium, magnesium, steel and titanium.

Due to their structure, bulk nanostructured metals and alloys exhibit different physical properties i.e. higher strength, higher corrosion resistance, and lower ductility than their conventional counterparts. To give an example, nanostructured nickel is 5 times harder than conventional nickel. This is because the properties of metals are governed by the Hall-Petch relationship - as grain size decreases, strength increases. Nanocrystalline materials are characterized by significant increases in yield strength, ultimate tensile strength, and hardness. For example, the fatigue lifetime can be increased by 200-300 % by using nanomaterials with a significant reduction of grain size in comparison with conventional materials.

Not only high strength but also high ductility is essential for the use of metals in automotive and aeronautics sector. Nanostructured metals normally have very limited ductility, but thanks to recent developments in the processing technologies it is possible to reduce ductility losses in nanocrystalline metals.

Besides the superior properties shown by nanostructured metals, their potential in the automotive and aeronautics applications is driven by their superior manufacturability properties too, such as in some cases the reduction of machining times and forging temperature, and the improved superplastic forming.

However, the current part sizes and volumes (and cost) that can be achieved are not sufficient to be used in most of the automotive or aeronautics structural parts, that is where nanostructured metal could have the highest impact.