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Recrystallization and Grain Growth in Nano-structured Austenitic Stainless Steel under Electric Current Heating
|Agnieszka T. Krawczyńska 1, Malgorzata Lewandowska , Roman M. Kuziak 2, Krzysztof J. Kurzydlowski 1
1. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland
Nanometals obtained by severe plastic deformation (SPD) exhibit very high strength combined with satisfactory plasticity. The microstructure of SPD metals can further be optimized by post-deformation heat treatment. In most cases, this heating is performed in radiation furnaces. On the other hand, it has been shown that heating by an electric current may significantly change the course of recrystallization and grain growth, due to the influence of the electric current on the migration of point defects and dislocations.
The aim of this work was to determine the influence of electric current heating on the process of recrystallization and grain growth in nano-structured metals obtained by SPD methods. Austenitic stainless steel 316LVM was used in this context for testing the efficiency of such a heat treatment.
Samples of 316LVM austenitic stainless steel were hydrostatically extruded, in a multi-step process with the total true strain of 1.84 to produce a uniform microstructure consisting of nanotwins. The twins averaged 19 nm in width and 168 nm in length. Earlier results proved that a post-deformation annealing at 700°C results in the formation of a recrystallized structure with nanograins of 68 nm in diameter. In the present study samples were heated to 700°C by alternating current, AC, for different periods of time using Gleeble 3800 thermo-mechanical simulator. Changes in the nanostructure of the AC annealed samples were investigated using transmission and scanning electron microscopes. Microhardness was also measured under the load of 200g.
The results obtained on the SPD samples of 316LVM austenitic stainless steels after conventional and AC heating are compared and discussed.
This work was carried out within a NANOMET Project financed under the European Funds for Regional Development (Contract No. POIG.01.03.01-00-015/08).
Presentation: Poster at E-MRS Fall Meeting 2009, Symposium H, by Agnieszka T. Krawczyńska
See On-line Journal of E-MRS Fall Meeting 2009
Submitted: 2009-05-11 15:22 Revised: 2009-06-07 00:48