I — ferrite

Fig. 10. Demagnetization curves of hard magnetic materials A, Nd2Fe B B, Sm(Co, Cu,Fe,Zr)2 C, SmCo D, bonded SmCo E, Alnico 5 F, Mn—Al—C G, Alnico 8 H, Cr—Co—Fe I, ferrite , bonded ferrite. To convert T to G, multiply by 10". ...

I ferrite/perlite to martensite I volume increase hindered by the bulk material... 

H-C-i Ferrite-Austenite Type Weldments , Metal. Mater., 38(2), 82-91 (2000), translated from Kovove Mater, 38(2), 116-129 (2000) (Transport Phenomena, Phys. Prop., Theory, 11) [2003Fuk] Fukai, Y, Mori, K., Shinomiya, H., The Phase Diagram and Superabundant Vacancy Formation in Fe-H Alloys tmder High Hydrogen Pressures , J. Alloy Compd., 348, 105-109 (2003) (Phase Relations, Experimental, 42)... 

Fig. 3.11 Structure of steels after cooling from elevated temperature as determined by composition. A austenite. At martensite and f i-ferrite (after Schaeffler)...

Purl] Purdy, G.R., The Dynamic of Transformation Interfaces in Steels-I. The Ferrite-Austenite Interface in Fe-C-Mo Alloys , Acta Metall, 26(3), 477-486 (1978) (Experimental, Phase Relations, Interface Phenomena, Kinetics, 23)... 

Ara] Arakcheeva, A.V., Karpinskii, O.G., Polytypic Relations in the Structures of the Group of Hexagonal Ferrites. I. Ca Ferrites of the Structural Type of Ca2Fei6025 , Sov. Phys. Crystal-logr., 33(3), 378-380 (1988) (Experimental, Crys. Structure, 5)... 

Figure 3 Picture of the inspected part (plasma-sprayed chromium cast iron on ferritic steel). The surface presents several cracks I to 15 pm wide.

There are three groups of stainless alloys (I) martensitic, (2) ferritic, and (3) austenitic. 

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. 

The ferritic steels may also undergo intercrystalline corrosion as a result of grain boundary carbide formation. In the normal softened state (treated i 800 C) the carbon is largely precipitated and the ferrite composition homogenised so that further heating at lower temperatures has no adverse effect. During solution treatment above 950 C, however, carbon is redissolved. Sensitisation can then occur at lower temperatures but the rate is so rapid that it can only be suppressed by very rapid cooling which is not practically feasible. Thus weld decay is very possible in service unless a remedial... 

Nodular graphite iron Nodules Pearlite or ferrite 3-3-3-9 <0-9 I-6-2-5 0-4 <0-01 <0-1... 

Potential-current density (E-i) curves, which have been determined for a number of the austenitic cast irons and also for the nickel-free ferritic irons, indicate that in general the austenitic cast irons show more favourable corrosion characteristics than the ferritic irons in both the active and passive states. 

In de-aerated 10sulphuric acid (Fig. 3.45) the active dissolution of the austenitic irons occurs at more noble potentials than that of the ferritic irons due to the ennobling effect of nickel in the matrix. This indicates that the austenitic irons should show lower rates of attack when corroding in the active state such as in dilute mineral acids. The current density maximum in the active region, i.e. the critical current density (/ ii) for the austenitic irons tends to decrease with increasing chromium and silicon content. Also the current densities in the passive region are lower for the austenitic irons... 

Table 3.51 Corrosion of Type I Ni-Resist and ferritic cast iron in acetic acid in laboratory tests at 15°C...

Times to failure for various stainless steels tested in MgClj have been shown to increase with increasing proportions of martensite present Perhaps the role of martensite under anodic dissolution conditions is comparable to that of ferrite in duplex stainless steels where the enhanced dissolution of one phase prevents crack initiation in the other. There is, of course, another aspect of martensitic transformation that should be mentioned, i.e. the transformation of austenite to martensite either in the bulk material or at a growing crack tip that can give increased susceptibility to... 

Sintered and sprayed ceramic anodes have been developed for cathodic protection applications. The ceramic anodes are composed of a group of materials classified as ferrites with iron oxide as the principal component. The electrochemical properties of divalent metal oxide ferrites in the composition range 0- lA/O-0-9Fe2O3 where M represents a divalent metal, e.g. Mg, Zn, Mn, Co or Ni, have been examined by Wakabayashi and Akoi" . They found that nickel ferrite exhibited the lowest consumption rate in 3% NaCl (of 1 56 g A y at 500 Am and that an increase in the NiO content to 40mol 7o, i.e. O NiO-O-bFejO, reduced the dissolution rate to 0-4gA y at the expense of an increase in the material resistivity from 0-02 to 0-3 ohm cm. 

Baranchikiv AE, Ivanov VK, Muraveva GP, Oleinikov NN, Tretyakov Yu D (2004) Kinetics of the formation of zinc ferrite in an ultrasonic field. Dokl Chem 397(Part I) 146-148... 

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