Introduction

The mechanical properties of two agglomerated powder specimens were investigated by low load indentation testing. The NanoTest was used, and this was equipped with an optical microscope capable of precisely positioning the diamond indenter on the area of interest.

The maximum load and displacement were set to 180 mN and 43 µm, respectively. The test probe was a Berkovitch diamond indenter. To perform a number of tests, particles were selected sequentially by means of the microscope and a test menu was defined for each one. The system was then left to automatically perform the scheduled indentation sequence.

Results

For Sample 1, very brittle indentation fracturing behaviour, shown as an abrupt depth increase in the load-displacement curves, was generally observed (Fig.1).

For Sample 2, a relatively high indentation fracturing resistance was observed, with the majority of the indented particles not cracking up to the maximum programmed displacement.

Figure 2

Clear differences were observed between the two samples, as shown by the maximum load data presented in Fig. 2. Here, the maximum loads achieved in a series of tests were sorted into ascending order and simply plotted for comparison. Such differences are highly significant when investigating and controlling powder processing and dispersion.

Figure 2 - Maximum load values achieved for Samples 1 and 2, showing that the indentation behaviour of the two specimens was significantly different.