NANO-INDENTATION USING SPHERICAL INDENTERS

Abstract

Depth sensing nano-indentation can be used to determine the mechanical properties of materials in situations where conventional test methods may be difficult or inappropriate to apply. Experimental materials may only be available in small quantities, as a component in a composite or as a coating on a dissimilar substrate. In this paper, nano-indentaticn techniques using spherical tipped indenters and a novel partial unloading technique are described from which an indentation stress-strain curve can be determined. These methods allow the elastic properties and plastic defonnation behaviour to be determined at the scale of the microstructure for metals, ceramics, glasses and components in a composite. The theoretical basis of the techniques are described using classical Hertzian mechanics. Examples are given of indentation stress-strain curves and of methods for determining the elastic modulus from both monolithic and coated materials. The high spatial resolution of nano-indentation allows the variation of properties from point to point on a material surface to be determined and presented as a mechanical property map.

keywords:

• Nann-indentation
• Spherical indenters
• Stress-strain curves
• Mechanical property
• mapping
• Yield behaviour
• Thin films