13 - Structure Formation and Mechanical Behavior of Two-phase Nanostructured Materials

Abstract

This chapter discusses the structure formation and mechanical behavior of two-phase nanostructure materials. The development of nanostructured materials has led to a new class of materials that are single or multiphase polycrystals with microstructural features, such as particle or grain sizes, layer thicknesses or domain sizes, in the nanometer range. Such nanostructured materials may contain crystalline, quasicrystalline, or amorphous phases and are characterized by an ultrafine microstructure, where the different phases are intimately mixed on a nanoscale. As processing techniques, both rapid quenching from the melt or solid state reaction can be utilized. These synthesis routes may directly lead to a two-phase nanostructure. In other cases, additional heat treatment has to be employed in order to create or optimize the desired nanostructure, such as in the case of devitrification of metallic glasses. Whereas crystallization of bulk glass-forming alloys can directly yield bulk nanostructured samples with the desired microstructure, rapidly quenched ribbons, gas atomized powders, or mechanically attrited powders and composites have to be subsequently consolidated to achieve dense bulk specimens.