Nickel-iron alloy contg. magnesium oxide - has a low coefft. of expansion and is used in bimetallic strips

摘要

alloy contains 0.015-0.6 wt.% MgO as an insoluble phase, uniformly dispersed in an alloy contg. 34.5-37.5 wt.% Ni, 0.03wt.% C and 0.15wt.% Mn. The alloy is prepd. by intimately mixing powders of Fe and Ni, in the desired quantities, with 0.015-0.6wt.% MgO, compacting to a coherent form, and heating in a reducing atmos. at 1035-1315 degrees C. A thermostatic element in the form of a strip, comprises a layer of the Ni-Fe alloy joined to a layer or double layer of an alloy(s) having a larger coefft. of expansion. The alloy has a very low coefft. of expansion and is resistant to grain growth making it suitable for use in thermostatic strips. The presence of the MgO augments its mechanical resistance and hardness, without requiring pptn. hardening, and without raising the softening pt. The alloy can also be used in precision instruments.