Melting point trends in intermetallic alloys

Abstract

We have examined the melting points of approximately 500 intermetallic binary alloys. We attempted to correlate the melting point behavior of the binary (1:1) alloys with a number of elemental variables including electron number, atomic size, orbital radii, electronegativity, etc. We find that a “Vegards's Law” of melting points works very well for predicting the melting points of binary transition metal alloys, i.e. the melting point of the alloy correlates with the linear average of the elementary melting points. However, this “law” works only moderately well for alloys involving simple metals. In addition, we find that transition metal alloys tend to have melting points below the averaged elemental melting points. This finding is in sharp contrast to simple metal alloys where the opposite trend is observed and it is indicative of fundamental differences between transition metal and simple metal binding. Finally, we have attempted to correlate deviations from a Vegard's law of melting with elemental variables. We found no strong correlation with elemental variables (or the heats of formation of the alloy in question) with the possible exception being a correlation with elemental volume changes upon alloying. The consequences of this correlation upon alloy design and metallic alloy formation are briefly discussed.