I have been doing alot of research recently on the use of Scandium Aluminium alloys. My employer is developing products using ScAl (not currently aerospace). Scandium is one of the rare earth metals so is attracting a bit of attention at present.
I am a recreational pilot and a (long time ago) Mechanical (Aerospace) engineer so I was fascinated to find out ScAl's aerospace history.
Alot of the work that was done was by the Soviet Union and China before the end of the cold war. The cost of producing Scandium (in $ terms and lives lost) was very high. The west had Titanium and the East had Scandium - problem was there was alot more easy to get titanium in the west than scandium in the east. There are small stock piles of Scandium Oxide being sold out of Russia and the Ukraine at this time, however it is about US$1200 per kg. Production from other sources (uranium tailings) is about 2-5 tonnes per annum.. 99.9% scandium metal is priced at around $80,000 per kg. The good news is you only need 0.5% to get the full strenght out of Aluminium so that only adds aound $80 per kg ($35 per pound) to the cost of Aluminium.
Scandium Aluminium is now used extensively in premium sporting goods (golf clubs, lacrosse sticks, baseball bats and fishing poles!) and high performance mountain bike frames. It is lower cost than Titanium Alloy and Carbon fiber.
It's very easy to get a yield stress over 530Mpa by just adding 0.5% Scandium - almost as strong as high tensile steel. If you are prepared to sacrafice a few other material properties, you can get it up to around 590MPa with other alloying elements (Mg,Si,Zn). It's weldable with no apparent HAZ, has excellent fatigue properties and can be cold and hot forged and cast using vacuum die casting.
In working with and researching Scandium Aluminium I have come across many urban myths that I am looking for information on. Apparently it was used in;
1. Soviet era fighters specifically the Mig 21 and most recently the Mig 29 and Mig 31.
2. Russian soyuz space craft (unsure which part) and Mir Space Station (again unsure which part)
3. R series submarine launced nuclear missiles nose cones (for punching through the polar ice cap).
Can anyone shed any light on this? I would be grateful for any insights.
Is anyone aware of it's use in any modern aerospace applications? I had heard that there were some experiments with doing "welded" wing skins using ScAl without rivets. I had also heard that some work had been done on ScAl for use in Air to Air missiles to replace titanium alloys to get the weight down so they can turn faster.
Thanks in advance for any info.
Chris (in Australia)
Dear Chris, (I hope that you are still in Australia)
I've been truing to find at least something for you in English , but failed. The best result was: http://www.lib.ua-ru.net/diss/cont/215376.html - this is a shop of sci- works. The link leads to 15 USD payment for the work, covering the following issues:
Process of laser welding of Al-Mg alloys with Li (1.5-1.75%) and Sc (0.15-0.3%) and how to achieve the best results in welding.
A part of this work was used at Sukhoy aircraft presentations in 2002 and at several further workshops. Plese let me know if you need any further assistance.
Here's some assorted information I managed to find:
-use in Mig 29: http://www.scribd.com/doc/17409218/Rare-Earths-Market (pg 7)
-Flightglobal archive about scandium in Uzbekistan: http://www.flightglobal.com/articles/1997/08/27/14887/central-asias-rising-star.html
-a lot of references here about scandium being used as part of an alloy
Hope this is perhaps of help :)