ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Severe Plastic Deformation (SPD) is known to be an effective method of producingnanocrystalline materials, for instance by HPT and ECAP. These techniques are also capable ofreproducing microstructures which arise naturally when high pressure and friction is involved, forexample in wheel-rail contact problems. The resulting deformation layers build the origin point forfatigue cracks. For that reason the knowledge of the mechanical properties of these deformationlayers are of vital importance. In the framework of this study a baintic rail steel quality wasdeformed by High Pressure Torsion up to distinctive equivalent strains at a nominal pressure of 6GPa up to a final equivalent strain of 16. Afterwards the evolution of the resulting microstructurewas investigated by Scanning Electron Microscopy, by microhardness measurements and X-raydiffraction. The bainitic structure showed a strong alignment and fragmentation into the sheardirection with increasing strain, which was accompanied by an increase in hardness as well. X-raydiffraction measurements showed that the amount of retained austenite decreases dramatically aftersmall amounts of strain, which indicates that retained austenite cannot be stabilized by highpressures. Torque measurements during deformation showed after strong hardening at thebeginning, a saturation behaviour for higher strains, whereas for instance pearlitic rail steel qualitiesshow further hardening
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.584-586.655.pdf
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