Phase transformations iron alloys

Martensitic phase transformations are discussed for the last hundred years without loss of actuality. A concise definition of these structural phase transformations has been given by G.B. Olson stating that martensite is a diffusionless, lattice distortive, shear dominant transformation by nucleation and growth . In this work we present ab initio zero temperature calculations for two model systems, FeaNi and CuZn close in concentration to the martensitic region. Iron-nickel is a typical representative of the ferrous alloys with fee bet transition whereas the copper-zink alloy undergoes a transformation from the open to close packed structure. ... 

Stable and metastable iron-carbon phase diagram. The behaviour of iron and iron alloys depends on the existence of its different forms and on their transformations technologically moreover the carbon content is crucial. These aspects are clearly shown in the iron-carbon phase diagram, especially in the low... 

As you can see, the process by which the iron-carbon alloy is processed and solidified is jnst as important as the overall stoichiometry. Although a discussion regarding phase transformations is more the realm of kinetic processes, it is nonetheless pertinent to snmmarize here the types of important ferrous alloys, particularly those in the cast iron categories. This is done in Fignre 2.13. 

Certain alloys of iron, nickel, and cobalt (Kovar, Fernico, etc.) have thermal expansion curves which nearly match those of borosilicate glasses, and a good bond may be formed between the two. Kovar is similar to carbon steel in its chemical properties. For example, it oxidizes when heated in air and is not wet by mercury. It may be machined, welded, copper brazed, and soft soldered. Silver solders should not be used with Kovar since they may cause embrittlement. At low temperatures Kovar undergoes a phase transformation, and the change in expansion coefficient below this temperature may be sufficient to cause failure of a glass-to-Kovar seal. The transformation temperature usually is below... 

Metallurgy was one of the first fields where material scientists worked toward developing new alloys for different applications. During the first years, a large number of studies were carried out on the austenite-martensite-cementite phases achieved during the phase transformations of the iron-carbon alloy, which is the foundation for steel production, later the development of stainless steel, and other important alloys for industry, construction, and other fields was produced. 

Sin] Sinha, A.K., Close-Packed Ordered AB3 Stmctures in Ternary Alloys of Certain Transition Metals , Trans. Met Soc. AIME, 245, 911-917 (1969) (Crys. Structure, Experimental, 16) [1971Sht] Shtolts, Ye.V, Yeshchenko, R.N., Influence of Hydrostatic Compression on Phase Transformation of an Iron-Cobalt-Vanadium Alloy During Deformation , Phys. Met Metallogr. (Engl. Transl.), 32(4), 207-209 (1971), translated from Fiz. Met Metalloved., 32(4), 876-878 (1971) (Experimental, Thermodyn., 6)... 

Tka] Tkachenko, I.F., Rusetskii, V.A., Gorbachev, A.F., Grigoryeva, M.A., The Phase Transformations in Iron - Manganese Base Alloys (in Russian), Izv. Vyss. Uchebn. Zaved., Chem. Metall, (7), 82-85 (1980) (Experimental, Meehan. Prop., 2)... 

Ric] Ricks, R.A., Howell, P.R., Honeycombe, R.W.K., Crystallographic Studies of Reaction Products in Isothermally Transformed Iron-Base Alloys , Phase Transformations. Spring Residental Conference. Inst. Metallurgists, Part II, 84-86 (1979) (Crys. Structure, Morphology, Experimental, 5)... 

Phase relations in the C-Fe-W system are of great interest above all because of the importance of tungsten as alloying element in steels. Therefore constitution of this system has been studied quite intensively. Other important aspects of this subject, in particular the dissolution of iron carbides during austenitization of tungsten steels, phase transformations of carbides as well as diffusion interaction of carbides with iron and steels also attract attention of investigators widely. Details of experimental studies of phase relations, crystal strac-tures and thermodynamics as well as applied techniques are presented in Table 1. 

Gol] Goldman, A.J., Robertson, W.D., A Correlation of Elastic Moduli, Supercooling and Heat Evolved in the Martensitic Transformation in Iron Alloys , Acta Metall, 13(4), 379-447, 391-401 (1965) (Thermodyn., Phase Relations, Phys. Prop.) cited from abstract... 

Iron contents up to 50% are used in some electroplated coatings, especially in Japan. In the United States, 12 and 18% iron alloys are used. Work by Goodwin (1988) showed that the as-plated 18% alloy is composed of a metastable phase. This transforms to equilibrium 7 phase when heated at 500°C for 2 minutes. 

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