Ferritic microstructures

The material properties used in the simulations pertain to a new X70/X80 steel with an acicular ferrite microstructure and a uniaxial stress-strain curve described by er, =tr0(l + / )", where ep is the plastic strain, tr0 = 595 MPa is the yield stress, e0=ff0l E the yield strain, and n = 0.059 the work hardening coefficient. The Poisson s ratio is 0.3 and Young s modulus 201.88 OPa. The system s temperature is 0 = 300 K. We assume the hydrogen lattice diffusion coefficient at this temperature to be D = 1.271x10 m2/s. The partial molar volume of hydrogen in solid solution is... 

Carbon steels are the most widely used materials of construction. Unalloyed carbon steels typically contain nominal amounts of manganese, silicon, phosphorus, and sulfur. They are normally supplied with a pearlitic-ferritic microstructure (see Figure 21.3) produced by air cooling a hot-formed product (e.g., hot-rolled plate) or by a normalizing heat treatment. They are available as either killed carbon steel or plain carbon steel. 

The influence of alloying elements (x) upon proeutectoid ferrite/microstructurally defined bainite formation in C-Fe-Mo alloys, where X is Co, Cr, Cu, Mo, Ni, Si, or V, which was examined in terms of the competing influence of the coupled-solute drag effect and the shifting in the paraequilibrium curve are discussed by [2004Aar]. 

Steels with a very low carbon content are characterized by a ferritic microstructure. With increasing carbon content a mixed structure of ferrite and pearlite forms. This structure is typical of structural steels. 

Studies to evaluate the effects of heat input and quenching on the surface of sensitized 304 material utilizing YAG laser and CO2 demonstrated that a remelted zone with a duplex austenitic/ferritic microstructure could be achieved to controlled depth of about 200 im. see susceptibility relative to the sensitized 304 material as evaluated by laboratory bent beam testing in simulated BWR environment was substantially reduced or eliminated. Solution annealing and desensitization of a region near the surface was also achieved with appropriate laser heat input controls [8.10-8.16],... 

AU other carbon steel, low-intermediate, and high-aUoy steels, ferritic steels Base metal Deposited weld metal and heat-affected zone (See Note 1) 2. Except when conchtions conform to Note 2, the material shall be heat-treated to control its microstructure by a method appropriate to the material as outlined in the specification applicable to the product form and then impact-tested. (See Note 1.) Deposited weld metal and heat-affected zone shall be impact-tested. 

The microstructure at position (ii) consisted of grains of ferrite and colonies of pearlite. It was noticed that the pearlite had started to "spheroidise" (see Problem 5.2). The microstructure at position (i) consisted of grains of ferrite and grains of lower bainite in roughly equal proportions. Estimate the temperatures to which the tube been heated at positions (i) and (ii). Explain the reasoning behind your answers. 

Fig. 20.49 Schematic illustration of some of the ferritic/pearlitic microstructures observed in hypo-eutectoid steels after various heat treatments...

An aggregate containing an alternate ferrite and cementite (Fe3C) lamellae microstructure. 

Baranchikiv AE, Ivanov VK, Oleinikov NN, Tretyakov DYu (2004) Microstructural evaluation of Fe203 and ZnFe204 during sonochemical synthesis of zinc ferrite. Inorg Mater 40(10) 1091-1094... 

Microstructure ferrite + acicular ferrite Yield stress low... 

Microstructure ferrite/acicular ferrite + small quantity pearlite Yield stress high... 

In this chapter the technological development in cathode materials, particularly the advances being made in the material s composition, fabrication, microstructure optimization, electrocatalytic activity, and stability of perovskite-based cathodes will be reviewed. The emphasis will be on the defect structure, conductivity, thermal expansion coefficient, and electrocatalytic activity of the extensively studied man-ganite-, cobaltite-, and ferrite-based perovskites. Alterative mixed ionic and electronic conducting perovskite-related oxides are discussed in relation to their potential application as cathodes for ITSOFCs. The interfacial reaction and compatibility of the perovskite-based cathode materials with electrolyte and metallic interconnect is also examined. Finally the degradation and performance stability of cathodes under SOFC operating conditions are described. 

Figure 5.29. Fe-rich region of the Fe C phase diagram. Stable Fe-C (graphite) diagram solid lines metastable Fe-Fe3C diagram dashed lines. The following current names are used ferrite (solid solution in aFe), austenite (solid solution in 7Fe) and cementite (Fe3C compound). Pearlite is the name given to the two-phase microstructure which originates from the eutectoid reaction ...

A relative decrease in Tafel slope has been observed with steel subjected to thermal treatments leading to different microstructures [274]. In this case an effect can indeed be expected because of the possible formation of different phases or different proportions (martensite vs ferrite) of phases (Fig. 10). An effect of the size of grains has been observed on the Tafel slope. 

Chemical compositions of the Fe-Ni specimens containing 90, 75, 50, 25, 20, 15 and 10 mass % Fe corresponded to nominal values within 0.5 mass %. At room temperature, the alloy specimens consisted of the a-phase (ferrite) at nickel contents less than or equal to 25 mass % or the y-phase (austenite) at higher Ni contents, while at a temperature of 700 °C the specimens of all compositions had austenitic structures. Ferrite constituted the microstructure of the Fe-Cr alloy specimens (10 and 25 mass % Cr) over this range of temperature. 

Soft ferrites are used for the manufacture of inductor cores (pot cores) for telecommunications, low-power transformers and high-flux transformers such as television line output transformers, and as television tube scanning yokes (Fig. 9.17). The more important material characteristics for these and other applications are now discussed with emphasis on the influence of composition and microstructure. The review paper by A. Broese van Groenou et al. [9] and the monograph by E.C. Snelling [10] are recommended to supplement the discussion. 

Fig. 9.31 Dependence of the permeability of the ferrite Ni0 36Zn0 64Fe204 on frequency and microstructure S, normally sintered HP, hot-pressed (after [9]).

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