Jean-Denis Mithieux

Coupling Recrystallization and Texture to the Mechanical Properties of Ferritic Stainless Steel Sheet

Obtaining optimal mechanical properties for highly formable ferritic stainless steel sheet requires careful control over recrystallization and texture. This is, in some cases, hampered by the slow approach to final recrystallization associated with the disappearance of deformed grains with particular orientations. The important mechanical properties for formability (e.g. the yield strength and r-value) are thus strongly dependent on the final few percent recrystallization. In this study, it has been attempted to correlate the microstructure and texture of ferritic stainless steel sheet to its mechanical properties as measured in uniaxial tension. It is shown that careful consideration of the evolution of texture and microstructure with recrystallization may explain the observed trends.

(Fe, Cr)6Nb6Ox phase of the filled Ti2Ni type with × ± 0.75 in the quaternary Cr–Fe–Nb–O system

Abstract The effect of O on the phase equilibria in Nb–Fe–Cr alloys, more specifically on the formation of a Ti2Ni type phase, has been studied. Nb–xFe–yCr alloys with × = 37.4 – 41.4 at.%, y = 7.6 – 8.6 at.% were subjected to long term annealing experiments at 950 8C after oxygenation. The phases were identified and characterized using scanning electron microscopy, X-ray diffraction and wavelength dispersive spectroscopy. In the pure Nb-37Fe-8Cr and Nb-41Fe-9Cr alloys respectively a two phase equilibrium between (Nb) and l FeNb and a three phase equilibrium between (Nb), l FeNb and Fe2Nb are established. In the oxygenated alloys a Ti2Ni type phase with composition (Fe, Cr)6Nb6Ox appears mainly at the expense of the l FeNb phase. With respect to composition and crystallographic parameters the (Fe, Cr)6Nb6Ox phase has large similarities with the Fe2.4Nb3.6O and Fe6Nb6O phase. From wavelength dispersive spectroscopy measurements, it is concluded that × equals 0.75 when (Fe, Cr)6Nb6Ox is in equilibrium with (Nb), l FeNb and Fe2Nb. × is higher when this phase is in equilibrium with NbO. The structure of (Fe, Cr)6Nb6Ox is also analyzed with Rietveld refinement. This analysis reveals that Cr atoms partially replace Fe atoms only on the 16d site and not on the 32e site.

Microstructure Refinement of a Low Interstitial Ferritic Stainless Steel by Cold Rolling and Annealing of Martensite

Several studies have shown that recrystallization of cold rolled martensite results in low carbon steels with very fine microstructures. Correspondingly, these materials exhibit promising combinations of strength and elongation. Most of the work on this processing route has focused on low carbon steels (0.1-0.2wt% carbon) where the interstitial content may play an important role in the microstructure refinement. In this note we describe experiments performed on a low interstitial stainless steel containing 0.02wt%C. It has been possible to achieve materials with high strengths (UTS > 1 GPa) and significant uniform elongation (> 8%), however, the microstructures associated with these properties are very different from those previously reported for low carbon steels.

Mechanical Behaviour of Ultra-Fine Grained Austenitic Stainless Steel

There is an increasing interest in the development of fine grained materials because this could appear as a solution for providing higher mechanical strength alloys, allowing thus reduction in component mass and raw material saving. The origin in the improvement of yield stress is directly connected with the the Hall-Petch relationship: n n

Recrystallization of stabilized ferritic stainless steel sheet

R_e = R_{e0} + frac{k} {{sqrt d }}

Stainless Steels for Exhaust Lines

n n(1) n nSeveral processes are now available for the elaboration of ultra fine grained materials among which grain refinement reached by the recrystallisation of a highly cold rolled material.