乡亲们
我有 有时 我曾写过一篇关于计算焊料合金密度的文章，因为人们对这个话题的兴趣比我想象的要大得多。最近，我突然想到将计算出的密度与一些合金的实际密度进行比较，看看正确公式的准确性如何（正确公式的推导见下文）。该公式假定 "完全混合"（即合金元素之间没有相互作用）。 我们研究的合金包括锡铋银合金、锡银合金、锡合金和锡铋合金。
To measure the density, I obtained a few alloys from Indium Corporation. My student, Evan Zeitchik, determined that a good technique to measure density is to machine the alloy into a rectangular parallelepiped (see photo), weigh it, and calculate its volume from its dimensions. The results agree with the correct formula to about 1 to 2 %. Some people would ask why there is any difference. The reason is that all alloys form different phases, and some form intermetallics. These phases and intermetallics would typically have different densities than that calculated for the alloy. I will have more detail on this work in a future post.
下面是正确密度公式的推导：
Many people incorrectly assume that if you have an alloy of x % tin and y % silver, that the density of this alloy would be 0.x*Density tin +0.y*Density silver. This intuitive linear formula is incorrect however, as density has two units (mass and volume). An easy way to understand the derivation of the correct formula (proposed by Indium Corporation engineer Bob Jarrett) is to consider a 96% tin, 4 % silver example.
假设我有 1 克这种合金，其中 0.96 克是锡，0.04 克是银。
锡的体积是 0.96 克/7.31 克/cc = 0.131327cc
银的体积是 0.04g/10.5g/cc=0.00381cc
因此，1 克合金的体积为 0.131327 + 0.00381 cc = 0.135137 cc
因此，它的密度是 1g/0.135137cc=7.39989g/cc
因此，一般公式为
1/Da = x/D1 + y/D2 + z/D3
Da = 最终合金的密度
D1 = 金属 1 的密度，x = 金属 1 的质量分数
金属 2、3 相同
该配方可持续使用 3 种以上的金属。
我开发了一个 Excel 电子表格，可以自动计算密度。如果有人想要一份拷贝，请给我发电子邮件：[email protected]
干杯，
罗恩博士
注：有趣的想法：历史上开采的黄金约有16.5 万吨。如果把这些黄金都集中到一个立方体中，边长大约只有 21 米。按 1550 美元/盎司计算，其价值为 8.5 万亿美元，比美国政府近 15 万亿美元的债务少得多。哎呀
