ISSN: 0090-3973
Page Count: 2

Short-Range Ordering in Nickel-Chromium Thermocouple Alloys

Pollock, DD
ProfessorMember of ASTM,State University of New York at Buffalo,NY,

Abstract

A short-range, lattice-ordering mechanism has been used extensively to explain the anomalous thermoelectric properties of such alloys as Chromel® and Nicrosil®. This concept appears to have had its origin in early crystallographic work that postulated this mechanism to explain experimentally observed changes in the relative electrical resistance of nickel-chromium alloys. Later crystallographic work, confirmed by several additional investigators, shows no evidence for the existence of short-range order in nickel-chromium alloys containing less than 25 At % Cr. Other investigators, reviewing the short-term thermoelectric deviations of these alloys, describe this mechanism as “much circumstantial evidence of a hypothesis that the short-term emf changes are due to short-range ordering in the Ni-Cr atomic structure of the Type KP thermoelement.” Since short-range ordering has not been established as being responsible for the thermoelectric properties of nickel-chromium alloys, this mechanism may not arbitrarily be considered as the sole rationale for their behaviors.

Keywords:
nickel-chromium alloys, clustering, thermocouples, Chromel®, Nicrosil®, short-range ordering, thermoelectric instability

Paper ID: JTE10684J
DOI: 10.1520/JTE10684J
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