Mechanical Behavior in the Micron and Submicron/Nano Range

Abstract

Throughout this book, there has been frequent discussion about the effect of size on the mechanical properties of materials. Usually, strength properties increase with decreasing dimensions, while ductility decreases. Decreasing the dimensions of a material may decrease the size of the grains in polycrystalline materials. The size of single crystals depends on their growth conditions, but, also in this case, decreased size has the same influence on the mechanical properties. The expectation of improved mechanical characteristics, especially in the submicron/nanometer range, however, must be supported by experimental evidence. Experimental evidence has, indeed, indicated the outstanding mechanical properties of nanocrystalline (NC) materials that often show: superstrength, superhardness, improved specific strength and tribological performance (as attested in the literature). This pattern of reduced ductility with increased strength is also indicated in materials having small dimensions; however recently, some cases of substantial ductility were reported in superstrong NC materials undergoing 100% elongation or more without failure. These reported properties, the unique combination of high strength and good ductility, make such materials ideal for applications in a wide range of fields, such as the aviation, automotive and electronics industries, to name just a few. The aim of this chapter is to provide an overview of some of the mechanical properties discussed thus far regarding materials with small dimensions and to characterize their observed behavior.