Dear Ahmad,

The kink bands are local deformation bands with an arbitrary degree of crystallographic rotation. This rotation usually increases with increasing the strain. In fact, some rotation takes place inside the kink bands during deformation. So, yes kinking can change the texture depending on the amount of deformation.

However, as you know, there is a specific misorientation angle between the twin and matrix (for example 50.5 deg. for {332} twins in beta Ti alloys). So, one can easily distinguish between them with an EBSD scan and measuring the variation of misorientation angle across the band.

The main difference is that kink bands are mediated by multiple slip plane events wheteas twins are coherent. Also the lattice rotation is a result of the deformation, not the other way about.

Thanks Nigel. Could you please explain what you meant by "Also the lattice rotation is a result of the deformation, not the other way about."? 

Is there any specific conditions for kink band to happen? For example twinning occurs in low SFE materials. What about kink band; is there any particular property which makes a kink band more likely to form? 

See if this paper can assist you:

http://www.sciencedirect.com/science/article/pii/S092702560900353X

Vikas my question is not about twinning, it is about its difference from kink band.

Dear Ahmad,

The kink bands are local deformation bands with an arbitrary degree of crystallographic rotation. This rotation usually increases with increasing the strain. In fact, some rotation takes place inside the kink bands during deformation. So, yes kinking can change the texture depending on the amount of deformation.

However, as you know, there is a specific misorientation angle between the twin and matrix (for example 50.5 deg. for {332} twins in beta Ti alloys). So, one can easily distinguish between them with an EBSD scan and measuring the variation of misorientation angle across the band.

Experimentally, I'd think X-ray diffraction topography/microscopy may be used to quantify the local (spatial) changes in orientaion between "kinks" and "twin boundaries". However, I'm not able to determine a method yet to verify this with mostly "as-grown" specimen analyses. Could this perhaps be the reason for the lack of Si (111) reflection on a mono-crystalline wafer specimen in certain topographic locations? Twinned substrate? Even the slightest "twist" may change the "optimal" Bragg condition. The low defect density in these specimen implies extremly narrow Bragg condition (rocking curve).

Very interested in this discussion/topic. Thanks to all contributors.

https://www.researchgate.net/post/How_do_I_figure_out_the_spatial_thickness_of_the_individual_layers_from_these_not_so_well_resolved_diffractograms

"Also the lattice rotation is a result of the deformation, not the other way about" - What about , in the case of equilibrium-grown mono-crystals?

"for example 50.5 deg. for {332} twins in beta Ti alloys" - Where do we find such data for materials like LiF, Si, GaN, GaAs, etc.? Meaning, twin systems mostly.

The challenge with electron microscopy is that, the sample prep may alter the lattice stress/strain condition in the specimen.

Deformation twinning and kink bands are entirely different deformation mechanisms with little in common except morphology. They may or may not co-exist in the same material system. Of course, this makes it necessary to have experimental techniques to distinguish between the two, which I will come to shortly.

First- twin formation is itself a deformation mechanism. Part of the crystal rotates into a mirror orientation, and this rotation is itself the deformation. There is a well-defined plane and direction for twinning, both being different from slip plane/direction.

On the other hand, kink bands form to facilitate slip. So the formation of the band is not deformation by itself; subsequent slip of dislocations along the band leads to the deformation. A crude visualisation is a walkway(kink bands) between two parallel roads(slip systems). Transport happens on the roads, the walkway just connects them. This is usually seen in anisotropic materials with few slip planes; hence most reported observations are in HCP crystals.

Coming to experimental distinction, Saeed has correctly pointed out use of SEM-EBSD. TEM-SAD will achieve the same goal over a shorter length scale, with higher precision. The key is that twins have a specific orientation difference from the remaining crystal (remember the mirror), while kink bands don't have a well defined crystallographic relation with the neighbouring matrix. We have recently used a combination of optical microscopy, EBSD and XRD to distinguish deformation bands (often considered a superset of kink bands) from other features with similar morphology:

https://www.researchgate.net/publication/321739520_A_micro-mechanism_to_explain_the_post-DRX_grain_growth_at_temperatures_08T_m?_sg=hdD92TiwQP7KMpHwCTL--CjGLmrxMAK2KGw8FU0CEVl3ULH9t3yaPvIOUhTf3pwxJVgFCjgd-qmeH8RlvV9kXy6kPe7njEMVsXr8YfCH.GTR2_opopn_-fcwwphxLxwNdSoreqwJKeBn6wBM-5Te9m6HvPvL4keCbpYgu9PkSEGIGeFYSEQJrTyxWXzlTzw

@Ravi - these two mechanisms are exclusively deformation related, and arise from the requirement to orient slip systems at a favourable angle to applied load. In case of crystal growth, the drivivng force is different, so these concepts may not be applied. I think the facets having preferred growth directions would determine the systems in your case.

see below paper on kink band

EBSD Study of Deformation Microstructure of an As‐Homogenized Austenitic Mn Steel after Hot Compression