Indentations in Nanophase Alloy

Application Note

Indentations in Nanophase Alloy - Micro-Hardness Mapping

Experimental

The specimen, which was mechanically polished, was in the form of a 10 µm-wide brazing alloy interface between two stainless steel surfaces. It was anticipated that the grain size would be extremely small, i.e., a nanostructure as opposed to a microstructure.

The NanoTest high resolution microscope and specimen positioning system were employed for accurately placing the indentations along the interface.

NanoTest operating parameters

Depth or load controlled	Depth
Total depth (plastic+elastic)	50 nm
Loading rate	0.1 mN.s-1
Dwell time at maximum load	0 s
Diamond	Berkovitch
Z distance between indentations	2 µm
Y distance between indentations	2 µm
Retraction between indentations	10 µm
Analysis method	Power law curve fit
Analysis parameters
Indenter geometry factor	0.75
% of unloading curve used	80
Depth resolution	0.033 ± 0.0001 nm
Load resolution	1.089 ± 0.023 µm

Results

As shown in the first figure, two phases were clearly discernible using relatively shallow indentations. However, deeper indentations produced an 'averaging' effect since several phase particles were indented simultaneously, i.e., at higher loads the individual phases could not be identified.

In the second figure, the hardness values have been sorted into ascending order to show the fractions of the two phases present