The low temperature magnetic properties of austenitic FeCrNi alloys. 3. The effect of chromium concentration in FeCr-17wt% Ni alloys

Abstract

The magnetic properties of ternary FeCrNi alloys containing 17 wt% Ni and 18–24% Cr have been studied over a range of temperature from 4.2–35 K by both ac and dc techniques in fields from 5 Am −1 − 6 MA m −1. At room temperature, the matrix of all the alloys was the paramagnetic fcc austenite phase (with an unavoidable 0.1 – 0.5 wt% δ ferrite) and on cooling all the alloys showed distinct peaks in ac susceptibility, though equivalent peaks in dc susceptibility were only observed at low fields in the alloy containing 18 wt% Cr. An analysis of the magnetization/field/temperature results showed that all the alloys were superparamagnetic at low temperature, due to the formation of ferromagnetic clusters in the disordered antiferromagnetic matrix, and that the chromium atoms make no measureable contribution to the magnetization of these clusters. Appropriate susceptibility values are tabulated for use as design data.