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National Repository of Grey Literature 2 records found  Search took 0.01 seconds. 
Crack Resistance Characterization in TiAl Intermetallics with Enhanced Toughness
 Dlouhý, Ivo ; Stratil, Luděk ; Fukutomi, H. ; Hasegawa, M.
The paper is focused on the analysis of the role of lamellar microstructure in fracture performance of model TiAl intermetallic compound. Coarse lamellar colonies and, at the same time, fine lamellar morphology were prepared by compressive deformation at 1553 K (region of stable alpha phase in TiAl equilibrium diagram) followed by controlled cooling to 1473 K (region of alpha+gamma phase) with delay on this temperature and then cooling down. The fracture toughness was evaluated by means of chevron notch technique. In addition, because of enhanced toughness, crack resistance curves were obtained by load - unload technique of pre-racked beams, namely in two directions of crack propagation relative to lamellar structure. Extensive development of shear ligament toughening mechanism was observed in fracture surfaces leading to quite good fracture toughness thanks to the heat treatment applied.
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Lomová houževnatost a mechanismy porušování intermetalika na bázi TiAl
 Dlouhý, Ivo ; Chlup, Zdeněk ; Hadraba, Hynek ; Kozák, Vladislav
The paper is focused on the analysis of the role of microstructure in fracture performance of TiAl intermetalics at room and elevated temperatures. Tensile properties, flexural strength and fracture toughness have been evaluated for Ti-40Al-2Cr-2Nb-1B and Ti-46Al-0,7Cr-0,1Si-7Nb-0,2Ni alloys. Positive Nb effect on fracture resistance was found; fracture toughness of the high Nb alloy was increased at contemporary increase of tensile and flexural strength. Fracture surfaces were evaluated using scanning electron microscopy showing the key role of mechanical twinning in deformation of both alloys. As a governing mechanism of the crack initiation a microcrack nucleation at boundaries between -TiAl grains was confirmed. Based on findings obtained key aspects of the effect of separate microstructural components have been discussed. Summary of toughening effects acting in this group of intermetalics has been provided.
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