What is an alloy called when it melts at the same temperature as something else? What is an alloy called when it melts at the same temperature as something else? For example, if there is an alloy that melts at the same temperature as glass then it will be susceptible to enameling and it is called an XXX-alloy.

As I recall, the term begins with the letters "eu-".
Isotectic substances are those which melt at the same temperature. 


Ref.: Heycock, C. T.; Neville, F. H. "On the freezing points of triple alloys of gold, cadmium, and tin". J. Chem. Soc., Trans., 1891, 59, 936-966

But be aware that this term is very rarely used.