乡亲们
I continue to get much interest in the solder alloy density calculator I developed some years ago. It is now online at https://www.indium.com/densityCalc/. It assumes no chemical interaction between the metals and no formation of interstitials. It works well for solder alloys.
Many people have an incorrect idea of how to perform this calculation. The most common incorrect concept is to multiply the %by weight of each alloy times its density and add them together . The correct derivation is below:
We want to find the density of an alloy composed of 3 metals. Assume the mass of the alloy is M. Metal A has a mass ma and a density da, Metal B has a mass mb and a density db and Metal C has a mass m c and a density dc. The total volume, V, of the 3 metals is va + vb+ vc, however since v = m/d, the total volume can be expressed:
1) V = ma/da + mb/db +mc/dc The density of the resulting alloy is D = M/V, hence 1/D = V/M, therefore:
2) 1/D = V/M = (ma/M)/da + (mb/M)/db +(mc/M)/dc
Now ma/M is the mass fraction of a, which we will call Xa, and similarly Xb and Xc for metals B and C.
方程2则变为：
1/D = Xa/da + Xb/db + Xc/dc，此即为我们的解。
该原理可适用于由三种以上金属组成的合金。
干杯
罗恩博士
