On Fri, 18 May 2012 12:03:42 -0500, Tim Wescott
wrote:

I've always been told that one of the cool things about hypereutectic
aluminum alloy is that its thermal expansion coefficient is significantly
lower than plain ol' aluminum, which makes it a handy material for
pistons. (The other cool thing being that all those silicon particles
can make for a hard, low-wear surface if you machine it correctly).

I was curious yesterday so I went prospecting on Matweb -- it listed
pretty darn near the same expansion rates for 2024 and an alloy with 18%
silicon. It also said the CTE was "derived from similar alloys on
Matweb", which makes me wonder what they mean by "similar". So now I
don't know what to believe.

Anyone know a handy chart of aluminum alloys and their coefficients of
thermal expansion? Google is not my friend in this: when I do a Google
search all I get are enthusiastic articles by gearheads like me. I can
learn all the stuff I already know about the virtues of the stuff, not
any engineering data about those virtues.

The ASM Metals Handbook Volume 2 covers it. For example:
alloy 380.0 11.8 × 10E-6 per °F
alloy 390.0 10.3 × 10E-6 per °F

I thought MIL-HDBK 5, which is freely available, might have some info,
but if it's in there I didn't see it.

IIRC, that's not much different from common wrought alloys.

--
Ned Simmons