THE ORIGIN OF THE 'INVAR' EFFECT,
ARMY MATERIALS RESEARCH AGENCY WATERTOWN MA
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The ideas of two electronic configurations of iron atoms in a f.c.c. lattice are extended to the iron-nickel alloy system. With a reasonable variation of the energy difference of these two configurations with nickel concentration it is shown that invar originates from the thermal ex citation of the configuration with lower atomic volume in opposition to the normal anharmonic source of expansion. The anomalous pressure dependence of the Vurie temperature and the variation of Curie temperature with concentration for alloys containing 30 to 60 Ni are also shown to follow.
- Properties of Metals and Alloys