Alumin(i)um question for UK members

In an old magazine, I read a mention of "Alcoa 946" aluminum alloy,
which is supposed to be more wear resistant than mild steel while
still easily machinable and with good corrosion resistance. I have
not been able to find any more details on this alloy, and Alcoa here
in the States has never heard of it (and does not use a numbering
system like that).

Does anyone in the UK know what this alloy might be? I'd like to find
out at least the composition to compare with what might be available
here in the US. I have the feeling it might be one of the marine
alloys.

Thanks,

Randy