Determination of mechanical properties of nanocrystalline materials by means of acoustic microscopy : application of pure elements (Fe and Ti) and alloys (Fe-Cu)
Nanostructured materials are distinguished from conventional polycrystalline materials by their extremely fine crystallite sizes. Because of the extremely small dimension of the grains, a large fraction of the atoms in these materials is located in the grain boundaries. This confers special attributes to this class of new materials.
The elastic modulus of a material is related to the atomic binding forces and characterizes the elastic properties of the material under loading. Young modulus can be measured by sound velocity (Korn et al 1988, Kobelev et al, 1993, Sanders et al 1999), tensile testing (Korn et al 1988, Nieman et al 1991, Wong et al, 1994, Sakai et al 1999 ), nanoindentation (Mayo et al 1992, Mayo et al 1990, Fougere et al 1995) in nc-metals and nc-ceramics upon compacted powders.
Compared to conventional metal, the ratio E/E0 (where E and E0 represent Young’s modulus of nc-metal and conventional metal respectively) is very variable, usually weak, due to important residual porosity which is often not measured.
The objective of the present study is to determine mechanical properties and especially elastic modulus for nc-metals (Fe and Ti) and nc-alloys (Fe-Cu). Dense nanomaterials are necessary involving consolidation of small samples with high pressure.