I have a square piece of metal from a processor heat sink that looks a lot like copper. I'm trying to find the alloy composition but I'm not sure how.
I happen to have both a digital caliper and a milligram-precision scale. The piece has a rectangular shape so volume wasn't hard to find. The volume is 5.378 cm³ and the mass is 52.395 g, that gives a density of 9,27 g/cm³. The density of copper is 8.96, nickel is 8.91, zinc is 7.14, lead is 11.34.
If I use this formula (which may be wrong):
$$p = a \cdot p_a + b \cdot p_b$$
$a$ being the volume fraction and $p$ the density. The density is higher than that of copper, this means there has to be a metal with a density higher than copper in the alloy, maybe lead? Using the formula I get 87 % copper and 13 % lead by mass, looks a bit too much.
Is this a good way to find the alloy or an alloy doesn't have a density or volume proportional to that of its components?