Ferrous alloys microstructures

Wei, R.P. and Gao, M. Chemistry, microstructure and crack growth response, in Hydrogen Degradation of Ferrous Alloys, R.A. Oriani, J.P. Hirth, and S. Smialowska (Eds), Noyes Publications, Park Ridge, NJ, 1985, pp. 579-607. 

Bainite forms isothermally as an intermediate transformation product above but below the temperature of eutectoid decomposition in ferrous alloys. This product is a mixture of ferrite and carbide, which is distinctly different from pearlite (a eutectoid product), and is termed bainite in honor of E. C. Bain who first observed such microstructures in collaboration with Davenport (Davenport and Bain, 1930). Bainite also forms during continuous cooling. Bainite transformations occur not only in ferrous alloys but also in non-ferrous... 

We may also use the method of tint etching to produce color contrast in microstructure. Tint etchants, usually acidic, are able to deposit a thin (40-500 nm) film such as an oxide or sulfide on specimen surfaces. Tint etching require a very high-quality polished surface for best results. Tint etching can also be done by heat tinting, a process by which a specimen is heated to a relatively low temperature in air. As it warms, the polished surface is oxidized. The oxidation rate varies with the phase and chemical composition of the specimen. Thus, differences in the thickness of oxidation films on surfaces generate variations in color. Interference colors are obtained once the film reaches a certain thickness. Effectiveness of heat tinting depends on the material of specimens it is effective for alloy steels and other non-ferrous metals and carbides, but not for carbon or low alloy steels. 

Reprinted with permission from Vend, A., Mrdak, M., Cvijovic, I., 2006. Microstructures and trihological properties of ferrous coatings deposited hy APS (Atmospheric Plasma Spraying) on Al-alloy substrate. FME Trans. 34, 151—157 Leeuwenburgh, S., Wolke, J., Schoonman, J., Jansen, J., 2005. Influence of deposition parameters on chemical properties of calcium phosphate coatings prepared by using electrostatic spray deposition. J. Biomed. Mater. Res. A 74,275—284. 

Albright D.L. (1988) Relationship of microstructure and corrosion behavior in Mg alloy ingots and castings , in H.G. Paris and W.H. Hunt (eds). Advances in Mg Alloys and Composites, International Mg Association and the Non-Ferrous Metals Committee, The Minerals, Metals, and Materials Society, Phoenix, Arizona, January 26 pp 57-75. Alves H., Koster U., Eliezer D. (2(XX)), Eaivironmental Behaviour of Mg-Alloys , in E. Aghion and D. Eliezer (eds). Mg 2000, Proceedings of the second israeli International Conference on Mg Science and Technology, Dead Sea Israel, pp 347-355. 

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