Introduction

A nice example of how sensitivity and resolution is improved using CrossCourt to generate comparative Kernel Average Misorientation maps -or “KAM’s”. The KAM map has become a standard method for indicating small, relative differences in crystallographic orientation (angular misorientations) between neighboring points in the specimen. Traditional EBSD applications such as OIM by EDAX-TSL and INCA/AZtec by Oxford-HKL include this functionality as standard in their analytical packages. Often these maps provide indications of the results of elastic strain. Internal strains often show rapid change from point to point and if they go significantly beyond the elastic limit they will typically include dislocations within the sample volume indicated by crystal rotations and a higher value of the KAM.

Comparative KAM Maps

Figure 1 is a KAM map generated by CrossCourt with settings applied to match the resolution available to the user of traditional EBSD systems. These systems use the Hough Transform to measure the orientation of the crystal -to an accuracy of 0.5 degrees. Increasingly this level of detail is inadequate for particular types of materials research, especially when it comes to measuring elastic stress and strain. It turns out that the standard KAM is too noisy for these purposes and therefore a different approach is required. CrossCourt uses cross-correlation techniques comparing one EBSD pattern with another in order to generate its mapping data -including the KAM. Below is an example of the same dataset with new settings applied to reveal more information about the specimen.


 

 

 

 

Figure 1 Conventional KAM

 

 

 

 

 

 

 

Figure 2 High Resolution KAM

 

Figure 2 shows a High Resolution (HR) KAM map, enabling misorientation measurements to within 1/100 degree. As you can see from the image above, we are now able to reveal far more detail in the specimen in what appears to be three distinct regions of behavior within the field of view.

CrossCourt is able to utilize this level of information and apply it to materials stress and strain analysis. Please take a look at some of the other data on the website describing the features and application of stress and strain measurement using our software tool.

Data courtesy of Oxford University, UK.

 

Download PDFQuestions? Contact us