116 



BELL SYSTEM TECHNICAL JOURNAL 



Classification of the Alloys 



A convenient way of showing graphically the compositions of the 

 alloys of iron, nickel, and cobalt is by means of the composition triangle 

 in Fig. 1. The sides of this triangle represent the binary alloys of the 

 three metals, and points inside the triangle, the ternary alloys. 



70 60 



PERMENDUR_ 

 REGION 



IRON IN PER CENT 



100 







A 



Fig. 1 — Coniposition diagram for alloys of iron, nickel and cobalt. 



In this diagram the alloys of special interest because of their mag- 

 netic properties are indicated, and, for convenience, each group in 

 which the magnetic properties are similar has been given a specific 

 name. 



On the iron-nickel side of the triangle the permalloy region is indi- 

 cated. In this group several compositions have been developed for 

 commercial use in the Bell System. The method of identifying these 

 alloys consists of prefixing a numeral indicating the per cent of nickel; 

 for example, 45-permalloy contains 45 per cent nickel and 55 per cent 

 iron. To some of these permalloys small amounts of other metals also 



