The low temperature magnetic properties of austentic FeCrNi alloys: 1. The effect of nickel concentration in FeNi-20 wt% Cr alloys

✍ Scribed by L.A.A. Warnes; H.W. King

• Publisher: Elsevier Science
• Year: 1976
• Tongue: English
• Weight: 860 KB
• Volume: 16
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/0011-2275(76)90005-9

✦ Synopsis

The magnetic properties of ternary Fe-Cr-Ni alloys containing 20 wt% Cr and 11 -32 wt% Ni have been studied over a range of temperatures from 10 -300 K by both ac and dc techniques, in fields from 5 A m-1 to 6 MA m-~. Apart from small amounts o f ~ ferrite in some alloys, the matrix constituent at room temperature is the paramagnetic fcc austenite phase. On cooling to low temperatures all alloys exhibit peaks in the temperature dependence of ac susceptibility, but in the 20 Cr/11 Ni alloy this is superimposed on the effects of an irreversible martensitic transformation below 195 K. Although a quantitative analysis of the results enables appropriate Neel and Curie temperatures to be determined for the alloys, it also reveals that the changeover from antiferromagnet behaviour at 0 K, with increasing nickel content, is a very gradual process involving the formation of increasing concentrations of superparamagnetic clusters, the moments, numbers, and sizes of which have been determined in alloys containing 16, 18, and 20 wt% NL The practical consequences of these findings are discussed in terms of the application of stainless steels in cryogenic engineering and appropriate susceptibility values are tabulated for use as design data.