126 



BELL SYSTEM TECHNICAL JOURNAL 



8000 zl 



6000 5 

 < 



UJ 



4000 £ 



30 40 50 60 



NICKEL IN PER CENT 



60,000 5 



40,000 5 



20,000 < 



Fig, 



8 — Resistivity, initial and maximum permeabilities, and coercive force of iron- 

 nickel alloys. 



fairly high values of superposed d.-c. field, shown in Fig. 7, also favors 

 its use for some purposes. 



7 8. 5 -Permalloy 



Another alloy long used in the telephone plant is 78.5 permalloy. 

 Quenching develops a higher maximum permeability in this than in 

 any of the other permalloys. Initial and maximum permeabilities of 

 10,000 and 105,000 readily are developed. The hysteresis loss and 

 the coercive force of quenched 78.5 permalloy are minimum. The 

 saturation flux density of this alloy is between 10,000 and 11,000 

 gausses, and it is reached with a very low magnetizing force. The 

 rapid rise in the flux density of this alloy for small increments in the 

 magnetizing force and the low saturation flux density are shown in 

 Figs. 2, 3, and 4. 



