The subject of this master thesis is focused to the refining of the cast structure of gamma-TiAl–2Nb alloy using cyclic heat treatment and to the analysis of the grain refining mechanism. Structure evolution after applied cycles of heat treatment was characterized using light, laser and electron microscopy and using microhardness tests. Application of five heat treatment cycles during which two phase transformations (eutectoid and alpha-recrystallization reactions) repeatedly took place resulted in refining of the cast columnar structure having the mean grain size 512 microns to fully lamellar structure containing gamma and alpha2 phases having the mean grain size 229 microns. Lamellae thickness of gamma was not changed while the thickness of alpha2 phase decreased, up to 78 nm. Refining of alpha2 phase resulted in the increase of the microhardness by 20 %. The recrystallized cast structure obtained by cyclic heat treatment and the knowledge on the mechanisms of the refining the structure were compared with the literature data and were discussed in order to propose more efficient procedure for refining thermal treatment of cast TiAl alloys.
| Identifer | oai:union.ndltd.org:nusl.cz/oai:invenio.nusl.cz:230254 |
| Date | January 2012 |
| Creators | Vraspírová, Eva |
| Contributors | Němec, Karel, Petrenec, Martin |
| Publisher | Vysoké učení technické v Brně. Fakulta strojního inženýrství |
| Source Sets | Czech ETDs |
| Language | Czech |
| Detected Language | English |
| Type | info:eu-repo/semantics/masterThesis |
| Rights | info:eu-repo/semantics/restrictedAccess |
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