ISSN:
1551-2916
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Maschinenbau
,
Physik
Notizen:
High-temperature (1200–1550 K) mechanical-loss and shear-modulus measurements were performed on fine-grained magnesia- and magnesia/ytrria-doped alumina at low frequency (10−4−101 Hz), using a forced-vibration torsion pendulum. Anelastic and viscoplastic relaxation phenomena were observed, which may be associated with grain-boundary (GB) sliding and, consequently, may be dependent on the grain size and GB segregation of yttrium. The associated activation enthalpies were 800–1100 kJ/mol. GB precipitation of yttrium aluminum garnet led to enhanced mechanical loss and increased activation enthalpy. Viscoplastic deformation increased sharply as the amplitude of the applied stress increased above a “threshold” value of ∼3 MPa. The mechanical loss and creep rate of identical materials showed qualitatively similar dependence on the grain size and yttrium content. A possible micromechanism of mechanical loss could be the motion of GB dislocations, which is important for the accommodation process of GB sliding.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1151-2916.1999.tb02060.x
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