Al-Li 2000 series alloy out gassing Studies at IIT

N. Solomey, Physics Division

Philippe Nash, Material Science Division

21 Feb. 2003

Current knowledge of Al-Li 2195

• NASA has extensive knowledge and many internal reports for this alloy for:– Welding– Cryogenic

• There is no known knowledge about:– Out gassing with first use of the alloy– Thin wall structures for vacuum to air,

hydrogen or liquid cryogenics.– Radiation damage.

We are using the Molly Furnace in P. Nash’s Lab at IIT• Large volume vacuum tank

• Can quickly achieve 1x10-7 Torr

(lower if we pump longer)

• Has a special painted interior with low out gassing characteristics

• Water cooled vessel and support stand so that just the sample can be heated to 1250° F.

Want to study only out gassing

• This is a study of out gassing by:– pumping on the

sample to see • how low vacuum

can be reached

• shape of the curve while pumping

– out gassing after reaching a vacuum will increase pressure

• This is not a study of suitability of these materials for:– window to air,

– gaseous hydrogen or helium, and

– to liquid hydrogen or helium

Sample PreparationSample Preparation• Six samples number 1 through 6 of various

types of Al alloys 1 in2 were machined by Ole Miss. Univ. and send to us. We do not know what sample is which alloys.

• Each sample was cleaned with Ethyl alcohol and stored in a clean tray and handled with gloves.

• The Molly Furnace was baked out for 3 days at 1200 F.

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

Outgassing study

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0 20 40 60 80

Time [min.]

Pressure [torr]

Empty Sample 1Sample 2Sample 3Sample 4Sample 5Sample 6

Pump-down out-gassing study

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0 20 40 60 80

Time [min.]

Pressure [torr]

Empty Sample 1Sample 2Sample 3Sample 4Sample 5Sample 6

Studies First Conclusions:• Preliminary results are that we see a slight

difference between the samples and an empty tank.

• P. Nash suggest we consider:– Heating samples to 25% to 50% of melting point

to enhance out gassing.– Grind up the samples to small pieces making a

larger surface area to enhance out gassing.

• Put a residual gas analyzer on the vacuum pump to see what is coming off.

Other Interest:• Our main interest is:

– Out gassing during first use of these alloys so we do not contaminated interior of accelerating cavity.

– Suitability of these new alloys for use as thin windows with liquid hydrogen or helium on other side.

• NASA has an interest in these 2000 series Al-Li alloys for radiation studies. This is also of interest to us.