Carbon Distribution in Low-Temperature Isothermal Iron-Based Martensite and Its Tetragonality

Abstract

Оттиски доступны непосредственно от издателя Фотокопирование разрешено только в соответствии с лицензией 2016 ИМФ (Институт металлофизики им. Г. В. Курдюмова НАН Украины) Напечатано в Украине.

Quantification of the Dislocation Density, Size, and Volume Fraction of Precipitates in Deep Cryogenically Treated Martensitic Steels

“…Some work on tool steels has claimed that carbon atoms segregate to dislocations during the DCT [20,23,30,33,[35][36][37], and that it is these segregated atoms that contribute to the increase in carbides during the tempering process [28]. However, other arguments state that the carbon atoms are essentially immobile at the temperatures used in DCT [38,39] and that it is in fact gliding dislocations that capture immobile carbon atoms [4,40], and some work has reported an elimination of fine carbide precipitation as a result of DCT [41]. Therefore, it remains unclear what effect DCT has on the subsequent tempering behavior and carbide development, with a range of results being published [2,39,42].…”

Novel Hybrid Ferromagnetic Fe–Co/Nanodiamond Nanostructures: Influence of Carbon on Their Structural and Magnetic Properties

“…Component Martensitic Fe-Co(2), colored magenta in Figure 11a, can be attributed to iron atoms, which are distant third neighbors of the interstitial carbon atoms and are only slightly influenced by the presence of these interstitials. Components Martensitic Fe-Co(3), colored cyan, and Martensitic Fe-Co(4), colored blue in Figure 11a, respectively, correspond to iron atoms occupying the closest second-and first-neighbor positions of the interstitial carbon atoms, respectively, which, according to the literature, acquire octahedral Fe/Co coordination in the bcc Fe-Co crystal structure [40,43]. Finally, component Martensitic Fe-Co(5), colored orange in Figure 11a, acquires the lower B hf value of the set and is attributed to Fe atoms with an environment of two carbon atoms as nearest neighbors; such environments (iron atoms with two carbon atoms nearest neighbors) are more probable to appear in increased carbon interstitial concentrations according to relative binomial distribution models [46].…”

“…Taking into account the TEM analyses, which suggest the diffusion of carbon atoms in the structure of the Fe-Co NPs, we attribute these components to the iron atoms of a martensitic-type Fe-Co phase forming in the Fe-Co NPs. Each component of this set corresponds to a different iron neighbor environment forming around the interstitial carbon atoms, which induce tetragonal-type distortions in the Fe-Co cubic lattice [39][40][41]43,46]. Considering the detailed analysis of the structural properties and related MP of such iron sites emerging in the martensite structure given by Kurdyumov and Gavriljuk [39,40], we can ascribe certain atomic environments to this set of components.…”

“…Each component of this set corresponds to a different iron neighbor environment forming around the interstitial carbon atoms, which induce tetragonal-type distortions in the Fe-Co cubic lattice [39][40][41]43,46]. Considering the detailed analysis of the structural properties and related MP of such iron sites emerging in the martensite structure given by Kurdyumov and Gavriljuk [39,40], we can ascribe certain atomic environments to this set of components. In particular, component Martensitic Fe-Co(1), colored green in Figure 11a, acquires the highest B hf value of the set and describes iron atoms in crystal sites placed in dilatated Fe-Co crystal lattice positions at distances relatively far from interstitial carbon atoms.…”

“…% concentration). The formation of martensite occurs as the crystal structure undergoes the γ-to-α transformation over a limited range of thermal treatments (slow or rapid cooling, aging, or tempering), when the transformation takes place too quickly for the carbon atoms to diffuse in order to form either graphite or iron carbide (Fe 3 C); therefore, these C atoms are trapped in the octahedral interstitial sites [39][40][41][42].…”