Why does adding a higher melting point metal lower the melting point of alloys?

[mmwave]

It's no surprise that if I take a particular metal and 'add' atoms of a second metal that has a lower melting point that the Tmelt of the combination is usually lower than that of the pure metal.

But it seems surprising that if a reverse this, take a low Tmelt metal and add atoms of a higher Tmelt the Tmelt of the combination is even lower. In fact there is a minimum of Tmelt at the Eutectic composition.

Any insight into why adding a few percent of a higher Tmelt metal can lower the Tmelt of the combination?

 

[Integral]

Why is a difficult thing to answer.

I will never forget the day my Thermodynamic prof brought in 2 pieces of solid material, when he placed them together in the palm of his hand and forced them together, the alloy liquefied in his hand. (I believe it was Indium and Rubidium but am very uncertain (give me a break this was 1977!)

 

[RuiMonteiro]

You can find some information on a Gallium/Indium allow in this site. It´s very intersting.



Rui M.