The low temperature magnetic properties of austenitic Fe-Cr-Ni alloys
1976; Elsevier BV; Volume: 16; Issue: 11 Linguagem: Inglês
10.1016/0011-2275(76)90038-2
ISSN1879-2235
Autores Tópico(s)Hydrogen embrittlement and corrosion behaviors in metals
ResumoThe compositional dependence of the Néel temperature has been studied, from data derived by different techniques and by various authors, for 30 austenitic stainless steels or special Fe-Cr-Ni alloys whose compositions fall near the range of the AISI 300 series. A linear relationship enables the predicted Néel temperature, TN to be evaluated with an rms deviation of 3.5 K on the basis of the wt % of alloy constituents. The effect of alloying elements in lowering TN∗ increases in the order Cr, Ni, Mo, and Si, while Mn is unique in raising TN∗. By comparing this equation for TN∗ with previous equations to predict the onset of a martensitic phase change at a temperature Ms, it is concluded that isotherms for Ms in ternary Fe-Cr-Ni alloys should also be parallel to the tangent to the boundary between fcc and bcc phases calculated from thermodynamic data. This conclusion throws doubt on the applicability of the Eichelman and Hull equation to the 300 series of stainless steels. If γ phase stability is achieved by adding Cr, Ni, Mo, or Si, the alloys are likely to be ferromagnetic at low temperatures, but if structural stability is due to C, N, or Mn, then the alloys should be antiferromagnetic or superparamagnetic. A logarithm plot of the maximum initial susceptibility versus Ni content can be used to estimate Xv max in the AISI 300 series stainless steels. This relationship does not apply to alloys with Mn > 2 wt %, but in these the value of Xv max is lowered. The significance of these observations is discussed in terms of the application of stainless steel in magnetic environments at low temperatures.
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