. The Bell System technical journal . id solutionabove the magnetic transformation is non-ferromagnetic while the asolid solution is ferromagnetic. When alloys in the region of 25 percent nickel are cooled, the transformation to the ferromagnetic state isnot completed until temperatures below room temperature are the alloy is cooled until the ferromagnetic structure is obtained, thetransformation to the non-ferromagnetic state does not occur on heat-ing until the temperature has reached approximately 600° C. 16 BELL SYSTEM TECHNICAL JOURNAL Elmen ^^ has investigated alloys containin
. The Bell System technical journal . id solutionabove the magnetic transformation is non-ferromagnetic while the asolid solution is ferromagnetic. When alloys in the region of 25 percent nickel are cooled, the transformation to the ferromagnetic state isnot completed until temperatures below room temperature are the alloy is cooled until the ferromagnetic structure is obtained, thetransformation to the non-ferromagnetic state does not occur on heat-ing until the temperature has reached approximately 600° C. 16 BELL SYSTEM TECHNICAL JOURNAL Elmen ^^ has investigated alloys containing more than 30 per centof nickel which are characterized by great magnetic softness and havebeen called permalloys, ^^ the name suggesting high alloys in the region of 40-55 per cent nickel find industrial ap-plication as soft magnetic materials. They are used in telephone andradio transformers and telephone relays. An alloy typical of thisregion is the one containing 45 per cent of nickel. A curv^e ^ showing 1600. -00 0 20 I 40 f 60 faO 100 NICKEL - PER CENTFig. 5—The constitutional diagram of iron and nickel. the permeability of this alloy is plotted in Fig. 6. From the data givenon this curve, the material exhibits an initial permeability of 2000 anda maximum permeability of 16,000. Another alloy in this region is the one containing 50 per cent ofnickel which has been investigated by Yensen. He has applied thename Hypernik ^ to it. Yensen, by giving this material a specialheat treatment, obtained an initial permeability of 4000 and maximumpermeability of 70,000. MAGNETIC MATERIALS IN RELATION TO STRUCTURE 17 Arnold and Elmen ^^ have investigated in great detail the alloys inthe region of 70 to 80 per cent nickel. These alloys are used whereextremely high initial permeability is required. One especially in-teresting use is in the loading of submarine telegraph cable. An alloytypical of this region is the one containing per cent of
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