Thermodynamic Analysis for the Magnetic-Field-Induced Precipitation Behaviours in Steels

Abstract

Alloy carbide M23C6 plays a significant role in the creep strength of reduced activation steels. Experiments have proven that a magnetic field accelerates the precipitation of M23C6 at intermediate temperature. A scheme that combines first-principle calculations, Weiss molecular field theory and equilibrium software MTDATA is proposed to investigate the thermodynamic features of magnetic-field-induced precipitation. The calculated results reveal that the origin of the magnetic moment is the NaCl-like crystal structure. The magnetic field enhances the exchange coupling and stabilizes the ferromagnetic phase region. The external field influences the Curie temperature, thereby changing the magnitude and position of the maximum magnetic heat capacity, magnetic entropy and enthalpy. The strong magnetic field improves the stability of M23C6, and the theoretical results agree well with the previous experiment. The study provides a theoretical basis for the magnetic-field-induced precipitation behaviours in steels.

On the M23C6-Carbide in 2205 Duplex Stainless Steel: An Unexpected (M23C6/Austenite)—Eutectoid in the δ-Ferritic Matrix

“…Only the Cr-metallic atoms are therefore taken into account (K-Cr 23 C 6 ) in the representation of the atomic layers (Figures 10-13). The different colours refer to the 4 sites (a, c, f and h) occupied by the chromium atoms according to the Wyckoff notation [55,71]. the less dense are , , and ( ≡ ).…”

“…The carbon atoms (C) are located at the 24e sites [55] (Table 6). The M 23 C 6 carbide structure can also be described as a packing of polyhedra: cubooctahedral and cubic groups [67][68][69][70][71]. These atomic groups, labelled P and Q (Polyhedral and Stick Modes, CrystalMaker ® ) (CrystalMaker Software Ltd., Oxford, UK) constitute the motif of the fcc structure and are located at {0, 0, 0} and {1/2, 0, 0} site types of the unit cell [67][68][69][70][71], respectively.…”

“…The M 23 C 6 carbide structure can also be described as a packing of polyhedra: cubooctahedral and cubic groups [67][68][69][70][71]. These atomic groups, labelled P and Q (Polyhedral and Stick Modes, CrystalMaker ® ) (CrystalMaker Software Ltd., Oxford, UK) constitute the motif of the fcc structure and are located at {0, 0, 0} and {1/2, 0, 0} site types of the unit cell [67][68][69][70][71], respectively. The cuboctahedron is a polyhedron with 8 triangular faces and 6 square faces parallel to {111} and {001} planes of the unit cell, respectively.…”

Determination of the site preference on the structure, magnetism and mechanical anisotropy properties of Mo-containing alloy carbide M6C (M = Fe, Mo)

“…Molybdenum carbides can be used to enhance the resistance to static fracture of components steel, for example springs, bolts and power plant structural parts [4][5][6]. The carbides are mainly composed of M 6 C, M 3 C, M 23 C 6 and M 7 C 3 (M = Fe, W or Mo) [7][8][9][10]. M 6 C is an * Authors to whom any correspondence should be addressed.…”

Solidification of Immiscible Alloys under High Magnetic Field: A Review

“…In recent years, an important new technique called high magnetic field (HMF) processing has been applied to material processing as a non-contact method [12][13][14], especially during solidification [15,16], which contributes to the influencing of secondary particle migration/orientation [17] and liquid metal motion and convection [18,19] to achieve more accurate control over the microstructure of materials [20,21]. The development of superconductivity technology has made it easy to obtain HMF of 10 T and above, which has promoted the application of HMFs in materials science and engineering and is therefore regarded as a new opportunity in this field [22,23]. It is difficult to define a critical value of a magnetic field to express "high".…”