首页|Nondestructive analysis of solute carbon in the ferrite phase in dual-phase steels containing Mn or Si by mechanical loss measurements
Nondestructive analysis of solute carbon in the ferrite phase in dual-phase steels containing Mn or Si by mechanical loss measurements
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NSTL
Elsevier
? 2022 Elsevier B.V.As a development of an earlier attempt to determine the concentration of mobile carbon atoms in the ferrite phase in dual-phase (DP, ferrite + martensite) steels by means of mechanical loss measurements, which was made on binary Fe-C alloys [Honda et al., Solid State Phenom. 184 (2012) 87–91], we have investigated effects of Mn and Si on the mechanical loss profiles, aiming at establishing a method for quantitatively evaluating the distribution of carbon in practical DP steels. First we re-examined the effects of Mn and Si on the relation between the strength of the Snoek relaxation and the concentration of carbon in iron by measuring the mechanical loss of solution-treated, single-phase ferrite samples of dilute Fe-Mn-C and Fe-Si-C alloys. We then measured mechanical loss of ferrite + martensite two-phase alloys of various carbon contents, after equilibrating at a temperature where the material consists of ferrite and austenite, and then quenching. The concentrations of carbon in solution in the ferrite phase can be estimated from the observed magnitude of the Snoek relaxation peak, using the linear relation obtained in the first set of experiments, and correcting for the volume fraction of the ferrite phase. These estimates agree reasonably well with those expected from the compositions expected from the ternary phase diagrams, as in the previous case of simple Fe-C alloys. This renders the basis for determining the carbon concentration in the ferrite phase by measuring mechanical loss of DP steels with alloying elements. As another development, the properties of the characteristic mechanical loss due to the martensite phase have been studied. The mechanical loss, which steadily increase above room temperature, turned out to exhibit a maximum at 480–500 K. It is found to be a thermally activated relaxation, with the following parameters of the relaxation time: pre-exponential factor τ0 ? 10?14 s and activation energy E ? 1.2 eV. However, its magnitude does not show a simple linear relation with the carbon content, unlike the case of the Snoek relaxation in ferrite.
NSTL
Elsevier
