For Ti-6Al-4V, I performed EBSD test and got the following data: ti-hex: 92.02%;Titanium cubic: 3.78%.The sample hit ratio is 95.80%.I wonder if it makes sense to have so few cubic phases?Can you give me some advice on how to further determine the validity of the test results, thank you very much !
Hello, the phase content (alpha/betta phase ratio) strongly depends on heat treatment of Ti6Al4V alloy. Therefore, the contents of betta phase can vary generally from 4 to 12 vol. % . You can determine the phase composition by X-ray diffraction analysis and compare your EBSD data with XRD measurements.
Depending of the heat treatment temperature, the overall amount of alpha could be 100% (in this case as alpha prime martensite after quenching the alloy from above beta transus, beta volume fraction = 0) and go down to 85% (for a globular microstructure, 15% retained beta). Hence, any beta volume fraction in between is possible for Ti-6-4. To access the overall amount of alpha and beta phase, X-ray diffraction could be used to check your EBSD analyses.
Normally, people are not interested in the overall amount of alpha-phase in a titanium alloy. Therefore, the primary alpha volume fraction (the amount of globular alpha being present at annealing temperature in case the heat treatment is performed in the two-phase field) is measured. Typical primary alpha volume fractions are 5 – 85%. In addition alpha prime, secondary alpha (within the lamellar transformed beta structure in a bi-modular microstructure) and/or ternary alpha (additional alpha precipitations within the retained beta phase) could be present. To access the amount of primary alpha, people normally perform a point analyses in microstructure images.
Carsten Siemers First of all, thank you for your professional advice. I would like to discuss this further with you. The results of EBSD test and XRD measurement for two-phase mass fraction are usually different. For my results, the XRD results bring me a new trouble, that is, which result should be chosen by the phase percentage?
In addition, for "the amount of globular alpha being present at annealing temperature in case the heat treatment is performed in the two - phase field", is there any references? Thank you!
Dear Junzhou,
The major question is: Are you really interested in the total volume fraction of alpha or in the volume fraction of primary alpha? (Personally, I have never measured the total volume fraction as the technical relevance is limited.) In the latter case, I would neither use EBSD nor X-Ray diffraction together with a Rietveld refinement analysis. Here a standard point analysis at metallographic cross sections should do.
Information about primary alpha can be found in standard books, e.g. Lütjering, G. & Williams, J.C. (2007), Titanium, Berlin, Germany: Springer or Boyer, R., Welsh, G. & Collings, E.W., Eds. (1994), Materials properties handbook: titanium alloys. Ohio, USA: ASM International or by looking at the quasi binary phase diagram Ti + beta stabilisers (picture taken from H. Sibum, V. Güther, O. Roidl, F. Habashi, H.U. Wolf, C. Siemers: Titanium, Titanium Alloys and Titanium Compounds, Ullmann's Encyclopedia of Industrial Chemistry, Electronic Release, a27_095, Wiley-VCH, Weinheim, Germany, 2017) together with the leaver rule.
Kind regards
Carsten
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