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Aluminum Copper Alloy Experiment
vtsteam:
Quoting from that site, Andrew, this alloy may naturally harden somewhat, as well:
--- Quote ---Solution treating is typically performed in the 450 to 575°C (842 to 1067°F) range in air, followed by rapid quenching into cold water, hot water, boiling water (-T61 temper), water-polymer (glycol) solution, water spray or forced air. Natural ageing to the T4 temper will occur at ambient temperature for 2XXX, 6XXX, 2XX and 3XX alloys, with most reaching a stable temper after 96 hours. Artificial ageing in the 93 to 245°C (199 to 473°F) range is utilised to meet the T6 and T7X tempers.
Immediately after quenching from solution treating, all alloys are relatively soft and can be moderately formed or straightened if performed within a couple of hours. These alloys will naturally age harden at ambient temperature, with their hardness gradually increasing with time following quenching. This can be suppressed by refrigeration below about 0°C (32°F) if it is desired to form or straighten the material more than a couple of hours after quench. Cooling to below about minus 23°C (minus 10°F) or colder is required to retain the As-Quenched (AQ) temper for prolonged storage times beyond a few days.
For maximum formability prior to solution treating and ageing, these alloys must be fully annealed to produce a stable dead soft O temper by heating in the 400 to 425°C (752 to 797°F) range, then slow cooling (28°C or 50°F per hour or slower) to below 235°C (455°F), formed, then solution is treated and aged.
--- End quote ---
awemawson:
I had intended to make a form of Duralumin, which age hardens, but after the event I realised that my aluminium source, like yours, being pistons had silicon in them. Copper was about 4%, silicon unknown - I supposed now that I have my alloy tester I could sample it if time permits.
(Off to visit the JCB 803 digger at the digger hospital tomorrow - I suppose I have to take hydraulic oil rather than grapes and flowers :clap: )
vtsteam:
The particular alloy I was imitating is not iisted for solution treatment and aging to temper, but what the heck -- I heated a sample up with the torch, short of melting and plunged it. Now scratches 6061 t6 lightly. Will check it tomorrow to see if there is a change, how it machines, etc.
Jonfb64:
In the past I have added copper to the soft pure aluminium at about 4% which seemed to reduce shrinkage and produce harder ingots. I don't recall making anything with them but probably just chucked them in with other stuff cos in the early days I didn't separate my ally out into type.
vtsteam:
Hi John, thanks for the info.
I jumped the gun a little tonight and tried a scratch test of the heat treated piece again, and it has clearly increased in hardness in a little over 4 hours. It now clearly scratches 6061-t6 and all the aluminum samples both cast and extrusion that I've tried.
It scratches the un-treated aluminum copper alloy ingots as well.
The untreated ingots in turn will not scratch the 6061-t6 sample, so they have not increased in hardness by aging.
My conclusion is, the mix of piston material (with likely about 12% silicon) plus low silicon scrap extrusions (probably entirely 6061) to yield a probable 6% silicon content, plus the addition of 4% copper from clean anealed tubing yields an alloy which has similar hardness to 6061-t6 aluminum alloy.
Heat treatment with plunge can be used to increase the hardness of this alloy further, and aging also increases its hardness.
I'll try machining it tomorrow.
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