Influence of annealing on crucible-free float zone melted LaB6-TiB2 composites

Polycrystalline and textured eutectics LaB6-TiB2 were obtained by the floating zone melting (FZM) method for powders using polycrystalline (PC) and (111) single crystalline (MC) seeds. The phase composition, microstructure, crystallographic orientation, residual stresses and mechanical characteristi...

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Bibliographic Details
Published in:Journal of alloys and compounds 2017-12, Vol.729, p.749-757
Main Authors: Soloviova, T.O., Karasevska, O.P., Vleugels, J., Loboda, P.I.
Format: Article
Language:English
Subjects:
Annealing
Boride composite
Crack propagation
Crucibles
Crystallography
Directional solidification
Eutectics
Fracture resistance
Fracture toughness
Mechanical properties
Microstructure
Non-equilibrium phase
Optimization
Phase composition
Polycrystals
Polymer matrix composites
Residual stress
Residual stresses
Seeds
Titanium diboride
Zone melting
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Summary:Polycrystalline and textured eutectics LaB6-TiB2 were obtained by the floating zone melting (FZM) method for powders using polycrystalline (PC) and (111) single crystalline (MC) seeds. The phase composition, microstructure, crystallographic orientation, residual stresses and mechanical characteristics in PC and MC composites after FZM process and their changes during annealing were studied. It is shown that the annealing temperature and the exposure time necessary to achieve the equilibrium eutectic phase and optimum mechanical properties in PC composites are lower than in the MC ones. Crack resistance and hardness in PC and MC composites after FZM process are smaller than the values in the equilibrium state and this difference is due in part to the residual stresses in both phases. It is established that under optimal annealing conditions, it is possible to substantially increase the mechanical characteristics of PС and MC eutectics. Fracture resistance rises in 1.5–1.6 times and hardness from 14 to 15 GPa to 25 and 27 GPa in MC and PC composites, respectively. •Annealing decrease strain-stress state eutectic composites after float zone melting.•Release tensile stress leads to improved fracture toughness.•Establishment of the equilibrium eutectic phase due heat treatment.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2017.09.223