MAGNETIC MATERIALS IN RELATION TO STRUCTURE 



17 



Arnold and Elmen ^^ have investigated in great detail the alloys in 

 the region of 70 to 80 per cent nickel. These alloys are used where 

 extremely high initial permeability is required. One especially in- 

 teresting use is in the loading of submarine telegraph cable. An alloy 

 typical of this region is the one containing 78.5 per cent of nickel. 

 Magnetization curves for this alloy after two different heat-treatments 

 are compared with the curve for annealed armco iron in Fig. 7. In the 



70 000 



60 000 



50 000 



40000 



30 000 



20 000 



10 000 



2000 4000 6000 8000 10000 12000 14 000 



FLUX DENSITY IN GAUSS 



Fig. 6 — The permeability of 45 permallov compared with that of 78 permalloy — 



Pettiti\ 



air-quenched condition, in which the alloy is magnetically the softer, 

 typical values for the initial and maximum permeability are 7000 and 

 65,000, respectively. 



In comparing the properties of 45 per cent nickel and 78 per cent 

 nickel alloys with reference to Fig. 6, the initial permeability is higher 

 for the higher nickel alloy. Therefore, for very low magnetizing forces, 

 the higher nickel alloy is characterized by higher flux densities. For 

 higher magnetizing forces, the 45 per cent alloy has more attractive 



