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Kinetic and thermodynamic factors leading to dissolution of cementite in pearlitic steel subjected to severe plastic deformation under pressure
|Witold Łojkowski 2, Yulia Ivanisenko 3, Hans-Jörg Fecht 1,3|
1. Ulm University, Albert-Einstein-Allee 47, Ulm 89081, Germany
Mechanical alloying encompasses many different processes: high pressure torsion, mechanical milling, ECAP (Equi-Channel Angular Processing), shot penning, hydrostatic extrusion, and also friction processes taking for example place on the surface of railway rails. Besides structure refinement to the nano-scale these processes in many cases lead to phase transformations. For instance in pearlitic steels, they lead to dissolution of the cementite phase. In this paper we review shortly the thermodynamic and kinetic factors governing this process in particular and the formation of new phases during mechanical alloying and in general. It is shown how phase equilibrium is locally changed by high strains resulting from elastic incompatibility and nonequilibrium structures of the interfaces between precipitates and matrix. In addition, it is shown that mechanically induced flow of material can lead to accelerated dissolution kinetics. This process may be seen as wear at the interface between the precipitate and the surrounding it matrix.
Presentation: oral at E-MRS Fall Meeting 2005, Symposium I, by Witold Łojkowski
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-30 08:01 Revised: 2009-06-07 00:44