I am trying to do EBSD analysis of deformed beta titanium alloys but I have problem in indexing the deformation products. As the EBSD data base does not know the orthorhombic α″ phase, we had to create it. Therefore, I need to know the lattice parameters and Wyckoff Positions. I found some information in literature but I still have problem in indexing deformation products (martensite, twins and slip lines).
Do you have an Kikuchi pattern?
Dear Grzegorz: do you think the tiny substitution of Nb has any impact? I guess if you describe Ti with SOF=1 it won't change anything.
On the other hand, this orthorhombic phase is pseudo-hexagonal. If you change the space group to monoclinic you get a phase with the following lattice parameters:
a=2.980A, b=2.943A, c=4.695 and the monoclinic angle is gamma=120.4°. I would expect a lot of orientation misinterpretations in case of an orthorhombic phase, i.e. the IPF colors in a single grain systematically changes between at least three colors.
Try to put these parameters to phase list:
alpha "
Crystal system: Orthorhombic
Space group: C m c m
Space group number: 63
a (Å): 2.9800
b (Å): 5.0760
c (Å): 4.6950
Alpha (°): 90.0000
Beta (°): 90.0000
Gamma (°): 90.0000
No. Name Elem. X Y Z Biso sof Wyck.
1 NB1 Nb 0.00000 0.18100 0.25000 0.5000 0.0830 4c
2 TI1 Ti 0.00000 0.18100 0.25000 0.5000 0.9170 4c
It worked for XRD in Ti13Zr13Nb alloy.
My specimens have different chemical compositions so different lattice parameters of α″. I have found several information about the lattice parameters of α″. Among them this one (Ti-5553) would be near to our alloys:
a = 0.301 nm, b = 0.491 nm and c = 0.465 nm
The data I showed before is from Ti0.8Nb0.2 alloy but it was sufficient for xrd of different alloy. I don't know if chemical composition makes such a difference for EBSD probably you are using data for alpha phase for pure titanium but it works really well with other chemical compositions. I wonder what's difference for EBSD when you change lattice parameter. Another thing, what is domain size of alpha " isn't it too small for reflection EBSD?
As I mentioned the data was from martensite phase in Ti-5553 alloy. However, as you can see in the attached file, there are several unindexed points in the picture which are most probably martensite phase.
Do you have raw patterns from these white points, are good quality, have you tried recalculation with alpha " phase in phase list?
Dear Nolze, I have taken some kikuchi lines from a´´ and bcc phases so that we can prove the existence of the phases but the indexing is not so good yet.
Do you have one or more patterns? If they show bands clearly I can perhaps determine the lattice parameters, Bravais lattice.
I am enclosing two patterns and analyzed kikuchi lines from martensite regions. The bands are not so clear.
Could you check alpha-Ti? Hexagonal.
Both phases (the formally proposed orthorhombic, but pseudo-hexagonal phase) are practically identical.
Let us know the result.
Dear Saed Sadeghpour,
I am facing the same issue. I have the same lattice parameters but not the wyckoff positions of atoms in Ti-1023 and Ti-5553.
Kindly share your findings regarding the unindexed regions and also the wyckoff positions.
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