Indentation Technique for Determination of Mechanical Behaviour of
Nanomaterials (Bulk and Coatings)
Yu.V. Milman, S.I.Chugunova, D.V.Lotsko, W.Lojkowski*, I.V.Gridneva,
A.Golubenko
I.M.Frantsevych Institute for Problems of Material Science, Kiev,
Ukraine;
*High Pressure Research Center, UNIPRESS, Polish Academy of Sciences,
Warsaw, Poland
The majority of nanostructured materials are obtained as small
samples, and standard mechanical tests can't be used. In IPMS new
methods for characterization of mechanical properties (yield stress,
ductility, strain hardening coefficients, thermoactivation analysis of
plastic deformation process etc.) by indentation technique were
elaborated. These methods are used for characterization of mechanical
behavior of nanostructured materials (metals and ceramics) in the wide
temperature range using hot and cold hardness and nanoindentation
technique for both bulk materials and coatings.
The method of determination of hardness and microhardness has been
used for many years widely for evaluating the mechanical properties of
materials in both scientific-research laboratories and in industry.
However in recent years, the method of local loading of materials
(LLM) with a rigid indenter is being transformed from the method of
evaluating the mechanical properties into a method of determining a
set of mechanical properties (yield stress, strength, ductility,
Young's modulus, ductile-brittle transition temperature, fracture
toughness, construction of stress-strain curves, etc). On the one
hand, this is caused by the development of completely new devices and,
on the other hand, by the development of the theory of indentation of
materials. The development of the method of determination of
mechanical properties by LLM is of special interest for investigating
nanostructured materials.
Only LLM can be used to examine the mechanical properties of thin
coatings and surface layers and separate phase components of composite
materials, and also analyze the mechanical properties of different
zones of welded joints and other structures with the properties
changing through the cross section.
In this report, attention is given to the new methods of measuring
hardness and determining the mechanical properties by the penetration
of a rigid indenter into nanostructured materials. Special attention
is given to the application of diamond indenters, especially a
tetrahedral Vickers indenter and a trihedral indenters with different
angles at the tip.
The application of LLM for investigation of mechanical behavior of
nanostructured materials (Beilby layer on rails, superplastic alloy
Zn-22%Al, nanostructured Ni and quasicrystals) is shown.
|