Mechanics and Tribology of MEMS Materials - prod.sandia.gov ...

Fig. 5.2. Orientation imaging of a cross section from an unworn Ni surface: (a) Orientation map
with respect to the surface normal; the heavy black lines represent orientation changes
> 10° and thin lines represent orientation changes of 1° or less, (b) Stereographic
triangle with color key for (a), (c) Pole figure for the cross section of unworn material.
An SEM image of the 1000-cycle unidirectional wear track on LIGA Ni surface is shown
in Fig. 5.3. The sliding direction was from left to right. The friction coefficient rose from the
initial value of 0.2 to a steady state level of 0.6 within the first 100 cycles. The location of the
FIB cut on the wear track can also be seen from the SEM image. As can be seen from Fig. 5.3, a
cross section of the wear track was ion milled from the center of the track, parallel to the sliding
direction.
An ion-induced secondary electron SEM image of the substructure underneath the wear
scar clearly reveals the bending of the columnar grains in the direction of sliding (Fig. 5.4).
There also appears to be a fine-grained region near the top, i.e. right underneath the wear track.
Figure 5.5a is the orientation map of the substructure underneath the wear track. The colors once
again represent the orientations normal to the sample surface based on the color key shown in
Fig. 5.2b. This is an interesting area as there is a region that has a fiber texture
(designated by green) in the predominantly fiber textured material. The thick and thin
black lines represent grain boundaries and low-angle grain boundaries respectively, as discussed
for figure 5.2. Figure 5.5a clearly reveals two characteristic zones, each with its own unique
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