Hakaru Masumoto1, Hideo Saitô2 and Yutaka Sugai2
1Foundation; The Research Institute of Electric and Magnetic Alloys, Sendai
The mean thermal expansion coefficient in the temperature range from 20° to 50°C, and Young's or rigidity modulus at 20°C and their mean temperature coefficient in the range of 20° to 50°C were measured with annealed alloys of cobalt, iron and manganese, and the influence of the addition of nickel on the property was also examined to ascertain whether the theory of the small expansibility of Invar, proposed previously by one of the present investigators, is valid in the above alloy system, and whether the effect of the addition of nickel observed with the alloys of cobalt-iron-chromium, cobalt-iron-vanadium, cobalt-iron-molybdenum and cobalt-iron-tungsten systems can be observed with the alloys mentioned above.
In the ternary system of cobalt, iron and manganese, it was found that the temperature coefficient of Young's modulus showed its negative minimum value in the neighbourhood of the composition having the minimum thermal expansion coefficient, and the relation of the temperature coefficient of the elastic modulus to the alloying concentration was almost similar to that observed with each alloy system mentioned above, with the exception that the present alloys did not show any positive value of the coefficient. When 10% of nickel was added to the ternary alloys, the range showing a positive value of the temperature coefficient of the modulus began to appear. With an increase of the nickel content, the minimum value of the thermal expansion coefficient became smaller, and the positive maximum value of the temperature coefficient of elastic modulus larger, and the cobalt content in the alloy showing these characteristics was substituted by nickel in the same way as in the case of the alloys mentioned above, while in the quatornary system containing 10% nickel, the manganese content was deviated to a higher content than that calculated from the substitutional law which is valid for the elements of chromium, vanadium, molybdenum and tungsten; this deviation was explained by the fact that the microstructure of the alloys is not composed of an austenite or a mixture of austenite and ferrite, but of a martensite. Some alloys having a small temperature coefficient of elastic modulus were named ``Mangelinvar''.
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