A Study of Nanoindentation of Nanostructured Materials

Normal grain sized metals of aluminium, copper and 70:30 brass were extruded by the equal channel angular extrusion (ECAE) process to a total strain of #~17. It was found that grain structures of submicron- and nano-sizes developed in all the extruded metals. Electron backscatter diffraction analysis confirmed that a high volume of high angle boundaries existed in the extruded metals, showing development of a well established grain structure. The extruded structures were found to remain stable without significant grain growth in subsequent annealings at temperatures up to 200DGC. Nanoindentation measurements were performed to examine the mechanical properties of the materials. It was found that the hardness of the metals was much higher than the initial materials of normal grain sizes. The hardness enhancement was most significant in the copper-zinc alloy. Nanoindentation measurements revealed the mechanical characteristics of the metals, showing variations of the stiffness and elastic modulus in these materials.