OFHC Copper rolled at room temperature (in as rolled condition) showed presence of twins in the microstructure. Is there a method by EBSD or other to identify which type of twin these are? (Deformation or Annealing?) Meyers, 2001 (in link) showed that copper cannot twins at low strain rate so then how are these twins forming?
http://www.sciencedirect.com/science/article/pii/S1359645401003007
The morphology of annealing and deformation twins is quite different, as they do not results from the same process. You can maybe also have a look in Humphrey's book about recrystallization and recovery.
1. In the beginning investigate copper to rolling
2. Later Investigate after rolling
3. Compare the received results in the sizes, by quantity (on area unit) and crystallographic
Dear Rohit,
EBSD TSL OIM Analysis software allows creating a map that contains recrystallization twins boundaries. All You need to do is to right click a map, choose "Properties" and then in Boundary section add pre-defined twin boundaries (you may choose between primary and secondary recrystallization twins).
Dear Wojciech, I was able to use the TSL OIM software but it does not differentiate between deformation twin or annealing twins. It only picks up sigma 3 twin boundaries which may be of any type of the above mentioned twins. I would like to know if this can be picked up individually by using any analysis on top of the software. I would also like to know if there is any orientation relationship difference between in annealing and deformation twins.
Normally annealing twins then deformed look more curved than deformation twins appeared at a later stage of deformation, also VECTORIAL deviation from ideal twin misorientation is higher on (originally) annealing twins underwent longer deformation history.
At that an advice by T.Eterashvili is valuable (separately check pre- and post-deformation structures) and will help to get sure in which degree the above reasoning is true. More so that ann. Twins are usually thicker and keep this distinction both in pre- and post-... States.
From the crystallography view point, there is no difference in the annealing or deformation twins - all are {111} type in fcc materials. However, annealing twins forms during annealing of the sample or recrystallization and they are coarser (wider) while deformation twins form during deformation under external force and they are fine in morphology.
Distinction will be not on type {111} and on concrete indexes. And also in the sizes and on internal structure (morphology).
OIM TSL software doesn't help with differentiating between both types of twins. However, a post-processing of the EBSD map can help; based on the geometry of the twins or morphology of twin boundaries.
As mentioned earlier, the twin thickness usually gives a clear indication, so you can first partition a twin "daughter" map and afterwards partition them based on grain aspect ratio.
Otherwise, since the deformation influences the morphology of annealing twin boundaries making them more 'rough' compared to fresh sharp deformation twins, you can use something like a fractal analysis-based method.
This is all for automated methodology. For single high-resolution maps, I would go for a manual one-by-one examining.
Thank you all for the valuable answers. If anyone is still following this question, Is there a method to extract coherent boundaries (Sigma 3) or its fractions in TSL-OIM Analysis software?
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