First, there are some basic questions. Some are rhetorical.

Where are the C and N coming from? How large are the peaks? What conditions did you use? What EDS system and model did you use? What would the results for Ti, Al, and V be if the C and N was ignored/normalized out?

I hope you are using something like 10 kV for Vacc. You need 2x over-voltage for good excitation. 20 kV is overkill.

The system can make a difference. I recommend evaluating systems on real-world samples before buying. They can give different results for a variety of reasons. I don't suppose you were involved in that process, so you need to work with what you have.

I suspect if you ignored the C and N that your Ti-V-AL numbers would be closer. Most systems normalize to 100% and if you are finding C and N, then you have to give up a proportionate amount of Ti-V-Al.

So where are the C and N from?

C could be from coating. What did you use? My Oxford Aztec allows me to specify the coating material and then exclude it from the analysis. Being at the surface, it does not undergo absorption and can be exaggerated. Organic contamination can lead to even higher levels of C that should not be ignored. You may need to work on sample cleanliness.

"N" could be the Ti-L line instead of N-K. How does your system handle elemental identification? Does it show the goodness of the fit as you add or remove elements? Can it show how much of the peak is allocated to Ti-L and N-K?

Dear Nouman Ali ,

Warren Straszheim is right;

you should share some more details about your experimental parameters and the sample handling/preparation.

In addition you should share your EDS.

Thanks in advance

and best regards

G.M.

Is your instrument rightly calibrated? C could be present in a higher amount with respect to that contained in the alloy due to the sample support/coating used during the sample preparation. It seems to me that the biggest mistake is onto Ti. Its Ka is near to that of V, they can be easily distinguished in your spectrum?

I have not coated my Ti64 samples with any coating. Instead I have prepared them through standard metallographic steps and etched with Kroll's reagent before microstructure investigation through SEM/EDS.

Yes TiKa and V are easily distinguished by energy peaks at different angles.

Why Nitrogen and Carbon weight percent of 6% and 8% appeared in EDS weight percentage? At the same time weight percent of Ti, Al and V reduced to 75%, 5% and 3.5% respectively instead of 90%, 6% and 4% of theor nominal value? Kindly guide if you can understand any probable reason.

• Surface contamination or oxide layer – Presence of TiO₂ or environmental contamination affects EDS results.
• Carbon or gold coating on the sample – Coating material may not be detected or skew results.
• Poor sample polishing / rough or uneven surface – Causes X-ray scattering and inaccurate quantification.
• Incorrect ZAF or Phi-Rho-Z correction – Without proper corrections, EDS underestimates actual composition.
• Small analysis area (spot analysis) – May not represent the bulk alloy; could hit only one phase.
• Charging effects due to non-conductive surface – Leads to unstable beam and poor data.
• Detector calibration or system error – A miscalibrated EDS system gives wrong quantification

Chhatar Mewada, your suggestions are fair enough and true in general, but why do you suggest them in this case? I suggest they are tertiary answers. Nouman Ali has not provided anything to indicate they would apply. An actual spectrum would be very helpful. It could indicate that one or more of those things would apply.

I go back to my first suggestions and questions.

Where does the N come from? I still suspect that the N is really the Ti-L peak, but I can't tell without seeing the spectrum. If it is really N, it might be a nitrate compound left over from the Kroll's reagent. Was the sample not washed thoroughly enough after etching?

I generally do not advise etching when you will be performing EDS. It chemically reacts with the sample and does do on a preferential basis. If you have a multi-phase material, etching will alter the relative abundance.

Where does the C come from? Is it contamination from the etching, from cleaning, or from the SEM?

Is it from a carbon coating for conductivity? You say you did not coat the sample, but how are you examining it? Is it not mounted but just a bare sample? If it is mounted, what is the mounting material? Is it conductive? Did mounting material smear over the sample during polishing? If it is not conductive and you are using low-vacuum mode to eliminate charging, remember that the beam will scatter and may excite some of the mounting material.

I suggested that the problem comes from normalizing Ti, Al, and V down due to the presence of the other elements. That does seem to be the case.

Ti Al V Sum

90.0 6.0 4.0 100.0 Theoretical composition you provided

75.0 5.0 3.5 83.5 Your measured composition

75.2 5.0 3.3 83.5 Theoretical composition scaled to a total of 83.5%

89.8 6.0 4.2 100.0 Your measured composition rescaled to 100% (w/o C, N)

That re-normalized result looks like what you were expecting. Unless you are very careful with your EDS procedures, you should consider a V value of 4.2 indistinguishable from 4.0.

Dear Warren Straszheim, I have printed 5 samples through SLM, heat treated them at different temperatures each.

I have cut samples by EDM and mounted the samples in Bakelite for preparation and etched them with Kroll's reagent i.e. mixture of Nitric Acid, Hydroflouric Acid & water. I have washed the samples with flowing water from tap. After etching i have dismounted the samples from Bakelite by breaking bakelite by clamping them in a vice.

Sample average weight percentages as per EDS are as follows:-

Ti 75 %, Al 5%, V 3.5%, C 9% and N 7.5%.

I can share EDS spectrum and weight percentage in a while.

This is the EDS spectrum Warren Straszheim

Unfortunately N and C peaks (with everything below Al peak) where cut off of submitted spectrum. I strongly believe C could be dismissed as contamination of SEM-EDS system. But it should be mentioned that etching a specimen prior to SEM examination is rather bad idea.

Spectrum part below Al peak can be seen in the EDS.png data file with hints on the presence of low Z atoms.

But I wouldn’t dare to evaluate this quantitatively, because of a) the strong overlap of the peaks and b) strong x-ray attenuation in that region and other reasons.

I have performed the EDS on Ti64 powder and found that the C and N percentages are coming with different weight percentages at different particles in the range of 1-12%. Which suggest that the presence of these elements is randomly concentrated on some particles and not uniformly distributed throughout the microstructure. Thus we can calculated weight percentages of Ti, Al and V by neglecting the weight percentages of C and N. And we found right weight percentages of Ti, Al and V as per chemical composition of the powder. Thankyou all for helping.

A picture or two would be nice to show that effect. If the C and N levels are high in localized areas, they should also show up as darker spots in backscattered electron images. Do they? Are they on the surface or are they embedded in the material?

I would also be interested in seeing the flatness of the material. That would probably be best from a secondary electron image.

But, yes, you seem to have confirmed the earlier suggestion that C and N are extraneous. By avoiding them, or eliminating their contribution. You found the expected contribution.