Titanium alloys
 

My daughter is researching the Eurofighter Typhoon and it says some of the control surfaces are titanium-lithium alloy. What does the lithium add in this instance? Does it make the titanium less reactive or allow it to be more malleable?

I hadn't heard of this combo and am just curious.

Titanium is non-reactive, which is why it's used in medical applications. I have no idea about the alloy though. Maybe it's used in thrust vectoring control surfaces?

Does she not have access to The Google?

(sorry, pasted wrong link)

There isn't much on google as to why lithium is used in the alloy.

Titanium does not like to be quenched in water that has any chlorine or fluorine because it turns brittle.

It is used on the ailerons and slats, it doesn't have thrust vectoring. The canards are just titanium.

That's just a canard.

Quack. SmileWavy

I would guess the main benefit of a Ti-Li alloy would be better/increased strength-to-weight ratio. Titanium is almost 2x lighter than steel, but is almost 2x heavier than aluminum (give or take, depending on the alloys). Lithium is the lightest (lowest density) metal there is, so it would be like "adding lightness" while still maintaining good strength/toughness properties (?).

There are likely other benefits as well. It may aid in reducing crack propagation, reduce embrittlement, etc. Not sure on any of that, but I am sure the info is out there.

I've heard of Aluminum-Lithium alloy but not Titanium-Lithium alloy. Not saying it doesn't exist though.

I prefer good ol' reliable Ti6Al4V ELI

is it transparent?

I worked with aluminum/lithium alloys when I was an engineer. The product was lighter and nearly as strong as some other Al alloys. I'm guessing the purpose of including it in titanium is weight savings.

Don't most Li alloys get fizzy in water?

I'm actually a proper metallurgist but haven't touched light alloys in 20 years. (I love that Pu and U are treated as "light alloys" by some of the professional orgs)

Li might be used as some kind of strengthening agent by grabbing O to make precipitates for either aluminum-style precipitate hardening or just to junk up the grain boundaries to stop/slow high temp issues from grain growth and creep.

Or it's already explained in wikipedia? I've already been taunted that with matweb and wiki I'm obsolete in today's workforce. I don't care - I'm awesome with powerpoint so there's always management to look forward to...

Actually, that sound more familiar than titanium-lithium. I am guessing that is what the OP meant.

There is actually a Ti-Li alloy. It is rather new tech as the solubility of Li in Ti was only first scientifically investigated in the late 80's and the results published in the "Bullitin of Alloy Phase Diagrams" (can you say obscure?) in 1989, whereas our knowledge of working with Ti and its alloys go back to the days of the YF-12 and SR71. I guess as all things military go, we'll know what the benefit of the alloy is once projects get declassified, or when commercial applications come to light!

this stuff sounds like a neat new alloy
from https://news.ncsu.edu/2014/12/koch-high-entropy-alloy-2014/

Researchers from North Carolina State University and Qatar University have developed a new “high-entropy” metal alloy that has a higher strength-to-weight ratio than any other existing metal material.

High-entropy alloys are materials that consist of five or more metals in approximately equal amounts. These alloys are currently the focus of significant attention in materials science and engineering because they can have desirable properties.

The NC State research team combined lithium, magnesium, titanium, aluminum and scandium to make a nanocrystalline high-entropy alloy that has low density, but very high strength.

“The density is comparable to aluminum, but it is stronger than titanium alloys,” says Dr. Carl Koch, Kobe Steel Distinguished Professor of Materials Science and Engineering at NC State and senior author of a paper on the work. “It has a combination of high strength and low density that is, as far as we can tell, unmatched by any other metallic material. The strength-to-weight ratio is comparable to some ceramics, but we think it’s tougher – less brittle – than ceramics.”

My bad, I was in a hurry. Why are they called a duck wing anyway?

I will ask her again, but I thought she said Ti/Li. Could be she just misread it as well which wouldn't be uncommon for a 14 year old.