Alloying aluminum into lead?

[Jim]

Forgive my memory (or the lack thereof!) but did I see some discussion a while back about alloying aluminum foil into lead to harden it? I've looked but can't find a discussion on that.

[303Guy]

Jim, I think it was aluminium into zinc. Not sure why though. Lead is soluble in aluminum so why not the other way round? Percentages are quite low though and the lead is added to copper containing aluminum alloys for machinability - it's a lubricant and the copper alloys are very strong.

[sqlbullet]

It would work, but according to the phase diagram chart, the melting point of the alloy, even with a small percentage of Al in the mix, is going to be quite high. Looks like you are around 850° F melting point even for a 1% alloy.

[I'll Make Mine]

Aluminum/lead alloys are similar to lead/zinc; the solubility is quite low. Aluminum and zinc are almost completely miscible, but aluminum/lead has long been considered an "impossible" alloy because of the combination of density difference and low solubility.

What would you gain by alloying lead with aluminum, anyway? Possibly hardening with a cheap additive, but antimony and arsenic are fairly inexpensive (given the low percentages needed) and both mix very easily in lead (antimony requires special flux for initial alloying, but lead/antimony is easily obtained already mixed) -- plus they're both relatively dense compared to aluminum (i.e. they won't lighten the boolit from a given mold by anything like as much as aluminum would at the same content).