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[en] The microstructure and tensile properties at 973 K in 9CrODS steels were investigated with respect to various fractions of the residual ferrite from zero to 47 vol.%. The formation of the residual ferrite was discussed from a balance between a chemical driving force for α to γ reverse transformation and the oxide particle pinning force, while 0.04 mass% carbon sample could contain an equilibrium δ-ferrite. With increasing volume fraction of the residual ferrite, strength at 973 K increases but ductility decreases, which is attributed to the fact that the residual ferrite is harder than the tempered martensite
[en] Highlights: • Typical microstructure of F82H–ODS steel is observed. • The existence of a meta-stable ferrite phase in F82H–ODS steel is confirmed. • The microstructure can be modified by the coarsening of the oxide particles. • The relationship between the phase formation and oxide particles is revealed. - Abstract: For the reduced activation F82H–ODS ferritic steel developed as the advanced fusion blanket material, the structure control and phase formation mechanisms were investigated. The area fraction of the ferrite phase was reduced, when the specimens were annealed at 1250 °C for long enough time inducing oxide particle coarsening. The effect of oxide particles on α–γ transformation was investigated, and ferrite formation is ascribed to pinning of α–γ interfacial boundaries by the dispersed oxide particles. This ferrite is meta-stable, and designated as residual-ferrite
[en] The process of residual ferrite formation and resultant high-temperature strengthening in 9Cr-ODS ferritic steel was investigated by TEM observation, dilatometric measurement and thermodynamic analysis. Formation of the residual ferrite is dominated by a balance between pinning of α-γ interfaces and the α-γ reverse transformation, and α-γ reverse transformation is affected by dissolution of carbides into the γ-matrix at the AC1 and AC3 points. The fine size of oxide particles is responsible for the higher strength of the residual ferrite containing ODS steels.
[en] Heterogeneous materials are ubiquitous in nature and synthetic situations and have a wide range of important engineering applications. Accurate modeling and reconstructing three-dimensional (3D) microstructure of topologically complex materials from limited morphological information such as a two-dimensional (2D) micrograph is crucial to the assessment and prediction of effective material properties and performance under extreme conditions. Here, we extend a recently developed dilation–erosion method and employ the Yeong–Torquato stochastic reconstruction procedure to model and generate 3D austenitic–ferritic cast duplex stainless steel microstructure containing percolating filamentary ferrite phase from 2D optical micrographs of the material sample. Specifically, the ferrite phase is dilated to produce a modified target 2D microstructure and the resulting 3D reconstruction is eroded to recover the percolating ferrite filaments. The dilation–erosion reconstruction is compared with the actual 3D microstructure, obtained from serial sectioning (polishing), as well as the standard stochastic reconstructions incorporating topological connectedness information. The fact that the former can achieve the same level of accuracy as the latter suggests that the dilation–erosion procedure is tantamount to incorporating appreciably more topological and geometrical information into the reconstruction while being much more computationally efficient. - Highlights: • Spatial correlation functions used to characterize filamentary ferrite phase • Clustering information assessed from 3D experimental structure via serial sectioning • Stochastic reconstruction used to generate 3D virtual structure 2D micrograph • Dilation–erosion method to improve accuracy of 3D reconstruction
[en] Highlights: → Mn-Zn ferrite wastes were recycled through wet chemical route. → The Mn-Zn ferrite takes advantage over A102 made in Acme Electronics Corporation. → The novel recycling technology attained environmental, social and economic benefits. - Abstract: A novel recycling route using acid leaching, reduction, purification, co-precipitation and traditional ceramic process was applied to process the Mn-Zn ferrite wastes and prepare the corresponding high permeability soft magnetic product. Above 95% of Fe, Mn, Zn in the waste materials could be recycled in the form of Mn-Zn ferrite products through the hydrometallurgical route. The comprehensive properties of Mn-Zn ferrite prepared from wastes by this route have broader frequency characteristics, higher resistivity, lower loss coefficient and temperature coefficient as compared to the A102 product (Acme Electronics Corporation, Taiwan). Moreover, the cost of this recycling technology has economical advantage over the traditional ceramic process, which holds a promising industrial application.
[en] Influence of the formation of ferrite and accompanying carbides in martensite matrix on the tensile and Charpy impact properties was investigated for reduced activation ferritic–martensitic (RAFM) 9Cr–1WVTa steel. As the fractions of ferrite and carbide adjacent to the ferrite grain boundary increase, both tensile and Charpy impact properties deteriorated in as-normalized condition. In particular, the tensile strength and elongation decreased simultaneously, which is believed to be led by the localized deformation in ferrite which is softer than martensite, promoting the formation and growth of voids. In addition, the formation of ferrite was also detrimental to the Charpy impact properties regarding to the absorbed energy because the precipitation of carbides around ferrite were vulnerable to the nucleation and propagation of cleavage cracks. The degradation of tensile properties can be recovered by tempering, but the DBTT temperature still increases with presence of ferrite
[en] The effects of the ferrite/austenite orientation relationship (OR) on interphase precipitation in Fe–0.1C–1.5Mn–0.4V (mass%) alloy were investigated by using electron backscattering diffraction and three-dimensional atom probe. VC interphase precipitation in both sheet-like and random dispersions is obtained in ferrite without a near Kurdjumov–Sachs (K-S) OR with adjacent austenite into which the ferrite grows, while the number density of VC in ferrite with a K-S OR is far lower, indicating that a large deviation from the K-S OR is necessary for interphase precipitation in low-carbon steels
[en] The development of Co-ferrite nanocrystals, and bulk materials for magnetostrictive applications is reviewed. This includes magnetic and structural properties and also processing conditions which are of special importance to increase the magnetostriction as well as to achieve very fine Co-ferrite nanocrystals. The magnetic properties of a single crystal, where a field induced phase transition was found, are also presented
[en] Ferrite growth behavior in Fe-C-Mn alloys has been studied using controlled decarburization experiments. The recently reported transition from LENP (local equilibrium-negligible partitioning) kinetics, at lower temperatures, to PE (paraequilibrium) kinetics, at higher temperatures, is shown to behave self-consistently over a range of Mn contents and temperatures and long-lived intermediate states between LENP and PE persist over a well-defined range of temperature and composition. A simple model which quantitatively describes the experimental observations over a range of composition and temperature is proposed. A key feature of this model is the introduction of an alloying element capacity of the moving α/γ interface, XMn*. The introduction of this quantity is purely guided by the experimental data and, at present, there is no physically based method for calculating it. Once XMn* is defined, multiple-jump kinetic analysis quantitatively describes the experimental observations over an impressive range of growth behaviors.
[en] Bulk cash smuggling is a serious issue that has grown in volume in recent years. By building on the magnetic characteristics of paper currency, induction sensing is found to be capable of quickly detecting large masses of banknotes. The results show that this method is effective in detecting bulk cash through concealing materials such as plastics, cardboards, fabrics and aluminum foil. The significant difference in the observed phase between the received signals caused by conducting materials and ferrite compounds, found in banknotes, provides a good indication that this process can overcome the interference by metal objects in a real sensing application. This identification strategy has the potential to not only detect the presence of banknotes, but also the number, while still eliminating false positives caused by metal objects