Titanium

By Lawrence (*****)

Date 10-30-2003 12:56

6AL,

Sorry to disappoint but I don't know.

I'm waiting on a new copy of ASM Materials Guide Vol. 6 It has a great wealth on fillers and substitutions. (This is often available at your local library)

Best advice is if the call out is for ELI Don't substitute unless it's allowed in your spec.

By ssbn727 (*****)

Date 10-30-2003 12:59

Hi TIGal-4v!
For questions like these I usually visit the Titanium Metals Corporation's contacts page in the "Engineering Technical support" link page.
When you reach this page, they will have a form for you to fill out and a space to ask your questions... These people are excellent when it comes to responding back to you usually via e-mail when it comes to getting quick results.
http://www.timet.com/contactsframe.html This is the contacts page.
When you get there, you must click the "Engineering Technical support" page link, then fillout the form...

I'd do it for you but I've got some stuff to do today so, I apologize for not being more helpful. Anywho, please let us know what they came up with, regarding your question...I'm always interested in these types of queries!!! Good Luck and all the best!!!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By chall

Date 10-30-2003 18:42

Hello,

I don't know if this will help, but here it goes.

Ti-6Al-4V (AMS) is the common name for Ti alloy with a UNS #R56402[source CASTI - Metals Red Book, Nonferrous data, 3rd ed.]. ASME Section IIC lists the classification as ERTi-5 and states this is commonly refered to as 6-4 Ti.

Ti-6Al-4V ELI (AMS) is the common name for Ti alloy with a UNS #R56400 [source CASTI - Metals Red Book, Nonferrous data, 3rd ed.]. ASME Section IIC lists the classification as ERTi-5ELI.

In looking at the supplementary section of SFA 5.16, it appears that the ELI designator is used when notch toughness becomes necessary. We don't encounter Ti that often, but my gut feeling is this would cause me to allow the use of ERTi-5 or ERTi-5ELI when ERTi-5 was specified; and require the use of ERTi-5ELI if specified.

Charles Hall

By TiG6al-4v (*)

Date 10-30-2003 22:36

[deleted]

By rodofgod (**)

Date 10-30-2003 23:42

Hi all
ERTi-5ELI is a lower oxygen grade of Ti alloy! used in surgical applications etc! You are right in your defintion of 'ELI'

By TiG6al-4v (*)

Date 10-30-2003 23:55

[deleted]

By ssbn727 (*****)

Date 11-01-2003 00:33

Hi TIG6al-4v!
Extra Low Interstitial or ELI refers to lowering the amount of interstitial solid solution -a solid solution in which the solute (stranger) atoms of Oxygen, Hydrogen, Aluminum and Iron occupy positions in the host space lattice and by becoming part of the lattice, which as a result, distorts the lattice so in effect, this is ERTi-5ELI is really a different grade of Titanium technically speaking of course and the AWS should clarify this because there are only two commercially available grades of Extra Low Interstitials Ti6AL-4V. they are grades 23 and 24 w/ru...
They should really call this ELI variant of Ti6AL-4V of filler, ERTi-23ELI because that's the grade number (23) of Ti that stands for an ELI variant of Ti6AL-4V!!! To add to the confusion, there is also a variant of
Ti6AL-4V Grade 23 ELI that has ruthenium which is: Ti 6AL-4V ELI 0.1 ru or Grade 29 Ti... (Ruthenium is a cheaper alternative to Palladium although it requires twice as much of this element to achieve the same corrosion resistance)
(AMS 4954) (AMS 4956)
(Ti6AL-4V Grade 5) (Ti6AL-4V Grade23 (ELI))
(Composition, percent) (Composition, percent)
Oxygen max - 0.25, 0.13
Hydrogen max - 0.015, 0.0125
Aluminum - 5.5 - 6.75, 5.5 - 6.5
Iron max - 0.40, 0.25
Other (unspecific)
elements (each) - 0.1, 0.01

I intentionally left out all of the other elements that make up both of these grades of Ti6AL-4V because they are identical in percentages except for of course, the remaining amount of Ti which makes up the majority element of these Ti alloys...
As you can see, the differences in the percentages of the above listed elements and other (unspecific) elements in these two grades of
Ti6AL-4V reveal as to where the interstitials ("stranger" atoms) may originate from.
If you minimze just a small amount of these interstitials, you then minimize distortion within the lattices, therefore encouraging stable and consistent grain stuctures in the welds which increases toughness, fatigue strength and corrosion resistance...
This also should answer your first question about the differences between the two Ti alloy grades. The only other differences between these two different grades of Ti6AL-4V are the mechanical properties referring to Ultimate and yield strengths in the the chart below...
The one value that stood out is the differences in MPa's for the yield strengths of each grade of Ti. I would think that maybe because of the lower amount of interstitials in the grade 23(ELI) would account for this.

Ultimate Strength Yield strength
Grade 5: 130/895 (ksi/MPa) 120/428 (ksi/MPa)
Grade 23 (ELI): 120/828 (ksi/MPa) 110/759 (ksi/MPa)

Now your last question is more complex but, I would say that because of the increased toughness, fatigue strength and corrosion resistance, there is sufficient justification to use the ELI variant so that you would minimize the formation of interstitials in the grain structures of the weld metal itself... Hence insuring weld integrety!!!
Btw, none of these grades are accepted for ASME code construction yet!!! However, Grade 9, another "alpha-beta" Ti alloy designated as:
Ti 3AL-2.5V is now permitted for division 1 code construction.
This higher strength alloy could be considered for solid construction of certain large, high temperature pressure vessels like autoclaves used for pressure hydrometallurgy, or for high pressure piping systems where it's properties could lead to economy as far as service life is concerned...
I hope that I was able to answer your questions regarding the use of these various grades of Ti6AL-4V!!!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By rodofgod (**)

Date 11-01-2003 01:39

Hi all!

I think thats a pretty comprehensive answer!!
The addition of a couple of letters in the pre-fix, or suffix of an electrode may seem to mean little , until you dig into the chemical composistion of a weld, and then you find out what those extra letters mean!
We're talking two different materials here!
Unless I'm wrong again??

By ssbn727 (*****)

Date 11-01-2003 02:18

Hi Rodofgod!
You are ABSOLUTELY CORRECT my friend!!!
Thank you for your understanding!!!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By ssbn727 (*****)

Date 11-01-2003 02:15

Hi Rodofgod!
ELI = Extra Low Interstitials, this is referring to interstitial solid solutions which invade the host lattice and as result causes the lattice arrangement to distort... So exponentially speaking you've got some very bloated and unbalanced crystals that are formed because of this!!!
Thus, problems result in grain formation and in weld integrety!!!
Oxygen is'nt the only cause of this though as you'll see in an earlier reply I posted... Just thought I'd let you know...

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By GRoberts (***)

Date 11-01-2003 23:07

A little more comments on interstitial alloying elements:
(although my comments are more coming from the steel side of things, most of the info can apply to any metallic crystal structure, such as Ti)

Interstitial elements are elements that have small enough atoms that they can fit in between the normal lattice sites that are occupied by the main elements that form the crystal. (as opposed to substitutional alloying elements, which take the place of the main element at a lattice site) The main interstitial elements for steel are Carbon, Nitrogen, and as mentioned earlier for Ti, also oxygen, and hydrogen which damages both. Interstitial elements can either be both helpful and damaging. Just because a metal/weld contains interstitial elements, does not mean anything by itself as far as properties. When interstitial elements are in solution, they are generally considered to be helpful by distorting the crystal lattice. The distorted lattice makes it harder for slipping to occur, so the material is stronger. The main thing that determines what properties the interstitial elements help develop in the mateial are what form the interstitial elements take. Usually, they like to form compounds given the right circumstances, such as chromium-carbides when stainless steel is sensitezed or nitrides/oxides, etc. It is usually these things that do any damage, not the elements by themselves. Some compounds are usefull though, (like carbides in a wear resitant surface). In titanim, interstitial elements do both good and bad. Oxygen and Nitrogen increase strength, but toughness is sacrificed. The only interstitial element that is always bad (as far as I know), and we're not quite sure why although there are several theories, is Hydrogen.

A couple of examples:

The quantity of interstitial elements is important:
In steel weld metal, usually Oxygen is considered bad, as it formes oxides that serve as stress risers/fracture intiation sites beacuse they are hard and brittle and not coherent with the crystal lattice. But a small amout of oxides are benificial because they act as initiation sites for acicular ferrite (which is a tough type of grain structure) to form when cooling down throught the transformation temperatures, so toughness is higher than if no oxides were present.

The form of interstitial elements is important:
Interstitial free steel is used for deep drawing. Interstitial elements (N and C) are consdired bad since they distort the lattice and contribute to faster work hardening, and thus tougher forming. Ti and Nb can be added to tie up the C and N in nitrides and carbides that are no longer intersitial, so don't promote strain hardening anymore.

Kind of a rambling post, but I hope it helps.

By ssbn727 (*****)

Date 11-02-2003 15:07

Hi GRoberts!
No sir! You never ramble as far as I see it!!!
I always welcome your comments and am better informed when I do so!!!
Now, I do'nt know how the rest of the participants in this forum feel so I'll just speak for myself (I'm sure they think highly of you also, like I do)... I understand where you are coming from when you talk about the benefits or the pitfalls regarding the type, amount of interstitial elements or what I like to call them as "stranger atoms" and their resultant formation of interstitial solid solutions which occur in the manufacturing, heat treatment, welding and PWHT when one referrs to the ever increasing variety of Ti alloy grades used today!!!
I also agree with you that most of the info you posted can apply to any metallic crystal structure. However, Ti6AL-4V being an intermetallic structure (I meant to say compound that has a complex crystal structure), does the same apply with the combination of HCP, FCC and BCC structures that are found in the Ti6AL-4V... (HCP = Hexagonal Close Packed for Ti, FCC = Face Centered Cubic for Aluminum, Iron (at intermediate high temperature) and BCC = Body Centered Cubic for Vanadium, Iron (at room & near melting temperatures)?
Now, I know that the HCP crystallographic form refers to Alpha phase (generally found at room temp.), the BCC form refers to Beta phase (generally found above 883 C (1621 F)) and that Ti6AL-4V is considered an Alpha+Beta Ti alloy, but is the potential for an FCC form or crystal structure to develop within the intermetallic compounds, complex crystal structures during any of the transformation phases, one of the influences in the distortion of the intermetallic compound crystallographic forms and the possible increase in the formation interstitial solid solutions within the crystal boundries which would cause a weakening of those boundries or would they act as "the cement" that holds the crystal formations together in Ti? Is the reduction in the percentage amounts of certain interstitial elements (ELI) the reason behind the consistencies found in the "distorted" or modified intermetallic compound - complex crystal stuctures so that there is a lesser possibility of interstitial solid solutions migrating within these crystal boundries or is it for lessening the amount of interstitial solid solutions that nevertheless tend to migrate within those boundries?
I noticed that the Grade 23 ELI variant of Ti6AL-4V when compared to the Grade 5 chemical composition, shows that by decreasing the amounts of Iron, Aluminum, Oxygen and Hydrogen, the Grade 23 becomes ELI. There is no change in the percentages of nitrogen or carbon or any of the other elements that make up Ti6AL-4V Grade 5 or 23. I can see where the oxygen and the hydrogen act as possible detrimental interstitials and yet, I'm not sure about how the reduction in the percentages of the other aforementioned elements can play a part in reducing the amount of interstitials? Is it because, the reduction in the oxygen and hydrogen percentages enables a lesser amount of aluminum to be used as an alpha stabilizer or decreasing the amount of aluminum oxides and the reduction of Iron as in the amount of iron oxides? This sounds logical but is it so? Now that I think of it, BBS Grand Central should've also added a new category section for Welding metallurgy and Welding physics!!! Oh well maybe next time...
Look foward to your and anyone elses comments!!!

Respectfully,

SSBN727 Run silent... Run Deep!!!

By GRoberts (***)

Date 11-05-2003 05:13

SSBN727,
Wow, this really is getting deep. (as in the deep end of the pool, not deep as in you better be wearing boots) I don't know for sure if I understood all of your question, but I do have a question for you in clarification. (definitions can always get in the way if two people are talking about completely different things with the same words) When you say "intermetallic" as in "However, Ti6AL-4V being an intermetallic structure", are you meaning that Ti6Al-4V is made of intermetallic phases, similar to sigma or chi phases in stainless steel, or are you just referring to the dual phase system that exists, like in duplex stainless steel? From what I have seen, Ti6Al-4V is a dual phase alloy, which is what I think you mean. When you say intermetallic, I tend to think of the normally unwanted and typically brittle compounds/or phases that form in a solid solution under certain conditions.

As far as the specific Ti questions/comments, (again, I don't know that much about Ti specifically), I have never heard that an interstitial element performs different functions in one crystal structure than another. (i.e. an interstitial atom in solid solution is considered a point defect, which limits planes slipping and thus strengthens the material functions the same in FCC, BCC, BCT, or HCP), so I don't think Ti is different in that way. It seems that the effect of interstitial elements differs the most dramatically between metal types when they are no longer in solid solution because of saturation (precipitation) or forming of compounds. So I don't know what specific technical reasons why reducing the impurities in the ELI grade prevents problems, but I when the problem is caused, the atoms are not necessarily in interstital solution anymore, but may be forming compounds or other phases.

Also, when I was looking around at various ELI grades, the definition seemed to vary. Some just report reduction of oxygen to improve toughness, and some reduce C, N, O, and Fe. I did not happen find any that reduced Al though. In Ti6Al-4V, it seems that Al is used as an alloying element instead of a scavenger like it is used in steel. I don't have a free energy diagram handy, but I don't know if Al could scavenge anything in a Ti alloy as Ti has a high affinity for the interstitials also. I know in steel, TiN will form before AlN. Another more simple option for why ELI is called ELI even though Fe and or Al might be reduced is that it could just be a misnomer. Kind of like MIG welding with CO2. Another possible reason is, since the purpose of ELI is to increase toughness, and Fe is a beta promoter if I remember correctly, Fe might be reduced to promote more alpha which is tougher. (Please correct me if I got that backwards)

Well, probably enough rambling for the moment, but I know one thing if they did start a welding metallurgy forum as you suggest. It would be my favorite one. (unless of course I was having some unexplainable, frustrating, unbearable welding metallurgy problem at the moment.)

By ssbn727 (*****)

Date 11-05-2003 23:17

Hi GRoberts!

I noticed that I did'nt include the word "compounds" or "complex" when I mentioned intermetallic structures!!! I apologize for that!!!
Anywho, I have since corrected the previous questions regarding the term "intermetallic" so that everyone can get a better feel as to what my questions were alluding to... So in essence, I meant to type: "Intermetallic compounds with complex crystal structures"...
Permit me to clarify; If the atoms of a minor metal in the alloy are much smaller than those in the major lattice, they do not replace the atoms of the major metal in the lattice but rather locate in points between or in intervening spaces known as "interstices" in the lattice...
Hence, this type of structure is called an "interstitial solid solution"...
If the minor metal atoms in the alloy cannot completely dissolve either interstitially or substitutionally, they will form the type of chemical compound the composition of which corresponds roughly to the chemical formula. This results in the formation of mixed kinds of atomic groupings consisting of different crystalline structures. These are referred to as intermetallic compounds and have a complex crystal structure.
Each grouping with it's own crystalline structure is referred to as a phase in the alloy and the alloy is called a multi-phase alloy. With the individual phases seen and distinguished when examined under a microscope at extremely high magnification... I would guess that a constitutional phase diagram would be an excellent tool to determine all of the phases for this particular alloy...
Basically, what I wanted to know if Ti6AL-4V being an alpha - beta alloy meaning that only alpha and beta phases were present or - does is it become a multi-phase alloy after welding consisting of another phase in lesser quantity included within the a+b phases and that's why I brought up intermetallic structures when I should've included those three other words: compounds, complex and welding!!! (MUST GET SLEEP!!!)
Therefore, by limiting the amount of interstitials to be diluted into the weld, then the potential for developing intermetallic compounds afterwards in the weld is lessened so that toughness is'nt lost and in some instances, depending on the filler metal composition, toughness is increased and so is corrosion resistance with a slight loss of ultimate strength...I'm guessing here so who knows, I may be off course a bit here!!!
Am I now making sense with this conundrum??? (MUST GET SLEEP!!!!!)
I'll have a clearer explanation from TIMET as soon as they reply to the questions I posed to them also so, do'nt worry about getting a thorough explanation, down to the atomic level as to why it's so necessary for the wire chemistries to have extra low interstitials in order to maintain or even improve notch toughness and corrosion resistance!!! As soon as I get the response from TIMET, I'll post it for everyone that may be interested... Until then, I'm getting some SLEEP!!!

Respectfully,

SSBN727 Run sleepy err, I meant silent... Run Sleep, I mean Deep!!!

By ssbn727 (*****)

Date 11-06-2003 00:37

Hi GRoberts!
Grade 5 has more aluminum than Grade 23 Ti 6AL-4V by about roughly .25%, Grade 23 being the ELI variant of Ti 6AL-4V according to the chemical compositions listed in Titanium Fabrication Corporation's webpage called "Titanium Specifications and Grades"
Here's the webpage:
http://www.tifab.com/subpages/tech_spec_grades.htm

Look for Table 5 which shows the relationship of the Noble metal grades to the Corresponding Titanium alloy grades then look at the chemical compositions below to see the differences in the chemical compositions between grade 5 and grade 23... I'm going to sleep now!!!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By ssbn727 (*****)

Date 11-06-2003 14:56

Good morning GRoberts and everyone else!!!
I finally got some good REM sleep so, hopefully this will translate in a better explanation as to why a filler metal with ELI (Extra Low Interstitials) in the wire chemistry are recommended to weld with Ti6AL-4V!!! Does anyone have the wire chemistry for AWS ERTi-5ELI by any chance???
I still have'nt recieved a reply to my query from TIMET but, as soon as I do I'll post it!!! I was looking at the RTI International website which has alot of info about Ti and it's alloy groups. RMI Titanium Company out of Niles, Ohio has Titanium Alloy Guide online that's in .html (for online viewing without adobe acrobat) or .pdf format so that you could download... Anywho, on pages 10 thru 11 is a basic Ti metallurgy section that is very easy to understand, Thank God!!!
Here's the webpage address:
http://www.rti-intl.com/products%20&%20services/index_ps.htm

Under the heading, "Effects of Alloying Elements" in paragraph 1. states; "Certain alloying additions, notably aluminum and interstitials (Oxygen, Nitrogen and Carbon) tend to stabilize the alpha phase, i.e; raise the temperature at which the alloy will be transformed completely to the beta phase. This temperature is known as the beta transus temperature"... Then it goes on to state in paragraph 2.; "Most alloying additions... such as chromium, niobium, copper, Iron, manganese, molybdenum, tantalum and vanadium stabilize the beta phase by lowering the temperature of transformation (from alpha to beta)...
Then it goes on to say that Tin and zirconium act as strengtheners of the alpha phase and have little effect on the transformation temperature so, Iron (Fe) only stabilizes the beta phase and aluminum tends to stabilize the alpha phase (I learn something new everyday!!!)...
The interstitials in Ti6AL-4V are O, N and C and not any of the other elements I previously mentioned so, basically in Ti6AL-4V grade 5 - there is a slightly higher percentage of Oxygen and Nitrogen (interstitials) in RMI's chemical composition compared to their grade 23 ELI variant of Ti6AL-4V but, no change in the Carbon content between these two grades... Funny how Titanium Fabrication Corporation's webpage lists a slightly different chemical composition for these grades as I suspected was the case so, I guess from manufacturer to manufacturer, there are some slight differences in their chemical compositions and their wire chemistries between their grade 5 and grade 23Ti6AL-4V ELI variant!!! I still do'nt know why the percentage of Hydrogen is reduced in the grade 23 ELI variant of Ti6AL-4V in Ti Fab's webpage which are different in RMI's grade 5 when you look at the differences in billet, bar and sheet - with the RMI grade 23 ELI having the same percentage of Hydrogen as the RMI grade 5 bar but, I'll find out soon enough even though as a rule of thumb -the less Hydrogen the better!!! There's also no change in the Fe percentages between the two RMI grades either but, slightly less in Ti Fab's grade 23 Fe percentage... There is a slight drop in the percentage of AL in the RMI grade 23 ELI variant as also is the case when you compare the RMI chemical composition and Ti Fab's Chemical compostion for grade 23 ELI variant of Ti6AL-4V, hmmm!!! I wonder if this also has something to do with the lowering of ultimate strength as a sacrifice for increasing notch toughness in grade 23 ELI variant of Ti6AL-4V when comparing the percentages of AL in grade 5 Ti6AL-4V???
Which brings up the question as to whether or not ASTM 4954 and 4956 are universally the same in their respective chemical compositions or their wire chemistries from manufacturer to manufacturer of Ti6AL-4V grades 5 and 23 ELI variants!!! So many questons, so little time!!!
anywho, these are my latest observations in finding out which are the actual interstitials that play a role in increasing notch toughness and corrosion resistance while at the same time sacrificing a small amount of ultimate strength when one compares the chemical compositions of grade 5 Ti6AL-4V and the grade 23 ELI variant of Ti6AL-4V...
The little voice that keeps nagging me inside my head wants to know if ASTM 4956 has virtually the chemical composition as grade 23 Ti6AL-4V ELI variant because if this is indeed the case, then the ASTM, AWS and ASME should revise their wire chemistries For ERTi-5ELI to become closer associated to grade 23 instead of grade 5 Ti6AL-4V... In other words, changing the grade number designation from 5 to 23 as in ERTi-23ELI...The only way to know for sure is to compare each organization's chemical compositions and wire chemistries!!! I guess I've gotta dive deeper!!!

Respectfully,

SSBN727 Run Silent... Run Deeper!!!

By Lawrence (*****)

Date 11-03-2003 13:51

I liked your explaination, In fact I'm copying the thing and will use it myself :)

Thanks