EDAX Hikari Super EBSD System and Gatan PECS™ II Broad Beam Ion Mill with APEX™ 2.0 Software
Ceramic or metallic coatings are frequently applied to strengthen or protect an underlying base material. Using EBSD to analyze the microstructure of these materials in cross-section demands that the contact between the coating and the substrate is planar, and that the true structure of each phase is continuous to the surface and undistorted.
Samples with porous substrate materials are particularly difficult to prepare due to the the additional risk of pulling out grains and maintaining the coarse polishing particles within the pores that can create scratches in the following polishing stages.
Materials and Methods
A porous ZnAl alloy with a dual-layer copper plating was positioned in the PECS II after routine mechanical polishing. It was then milled utilizing 5 kV Ar ions at a 3° incident angle for 30 min, and then by 60 min with 4 kV. The extended duration was necessary for an oxide layer to be removed from the ZnAl matrix material.
In the softer Cu coating, certain scratches can still be seen, but milling was stopped to reduce side-milling of the pores and coating. The surface of each material was flat and appropriate for EBSD mapping after milling.
Figure 1. (a) An SEM secondary electron image of the sample in a horizontal position. The two-layer Cu coating is on the left (b) SE image with the sample in a tilted position. The analysis surface is flat and produces good quality EBSD patterns. Some side-milling can be recognized in the pores. (c) An EBSD Image Quality (IQ) map of the ZnAl matrix. (d) An EBSD IPF map on a PRIAS™ bottom image of the ZnAl matrix. (e) A phase map on an IQ map and (f) an IQ map of the Cu coating. The two layers in the Cu coating can be recognized by the grain size. (g) An IPF on a PRIAS center map. (h) EBSD patterns of the ZnAl matrix and Cu coating. Image Credit: EDAX
Materials with a high strength or protective surface coating can be effectively prepared for analysis with EBSD through the application of broad beam ion milling. Care must be taken to reduce the side-milling effects of free pores and surfaces.
This information has been sourced, reviewed and adapted from materials provided by EDAX.
For more information on this source, please visit EDAX.