Cleavage fracture and the brittle-to-ductile transition of tungsten single crystals
- Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)
- Inst. of Solid State Physics, Chernogolovka (Russian Federation)
The fracture toughness of high purity tungsten single crystals is measured between 77 K and 600 K in 3-point bending. Precracked specimens of 4 different crack systems are used: cracks are injected on both the primary {l_brace}100{r_brace} cleavage plane and forced to propagate either along the <100> or along the <110> direction. In the low temperature regime the results allow to discriminate between the intrinsic brittle behavior and the contribution from plasticity. The authors find that brittle crack propagation is highly anisotropic with respect to the propagation direction. This can be interpreted as a direct consequence of the bond breaking process and is in contrast to the thermodynamic Griffith criterion, which does not discriminate between different crack propagation directions in the same cleavage plane. At higher temperatures the measured fracture toughness of the <110> crack systems is markedly higher than that of (100) cracks. However, the brittle-to-ductile transition (BDT) temperatures of all 4 crack systems do not vary significantly and are all at about T{sub BDT} = 400 {+-} 50 K. The dependence of the BDT temperature on loading rate gives an apparent activation energy of Q{sub BDT} = 0.2 eV.
- OSTI ID:
- 400599
- Report Number(s):
- CONF-951155--; ISBN 1-55899-312-6
- Country of Publication:
- United States
- Language:
- English
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