Main Question or Discussion Point
Who can calculate the meltingpoint for me of a mixture of metals with 40% Sn and 60% Pb?
Euhh, I have no clue what that means :) The substance I am asking for is soudage (a complete foreign word to me, I had to look it up in a dictionary)Originally posted by Bystander
From first principles? Or, did you just want a value for the Sn-Pb eutectic?
Originally posted by Monique
Ah! Thank you Bystander :)
But why is the eutectic temperature so much lower than the melting temperatures of the individual metals,
Melting points of even ideal mixtures aren't going to be a composition weighted average --- and, definitely not a mass/weight weighted average. The colligative properties of the components are going to control ideal mixture m.p.s, and interspecific interactions have to be taken into account for real mixtures.and why is my little calculation so far off?
I'll be picky and correct you here --- the eutectic is the specific composition at the lowest T on the phase diagram --- it can be considered the m.p. of a compound, Sn4Pb, and the compositions of both the liquid and solid phases are identical; the melting "range" for other compositions is the range of temperature over which the solid phase(s) melt to yield a liquid phase the composition of which varies as T changes.Pb mp = 372.5
Sn mp = 231.9
40/60 Sn/Pb eutectic temp 183-238