Fracture properties of interfacially doped Nb-A12O3 bicrystals: I, fracture characteristics

作者: D Korn , G Elssner , R.M Cannon , M Rühle

DOI: 10.1016/S1359-6454(02)00193-3

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摘要: Abstract The influence of orientation and impurities on the fracture behavior Nb–sapphire interfaces was studied using notched bending tests. Single crystals were diffusion bonded in UHV for different interface orientations. bicrystals doped to produce prescribed fractional interfacial coverages Ag. impurity content measured after with Auger spectroscopy. tougher exhibit significant nonlinearity loading. A J-integral analysis used account large plastic zones. For undoped at 1400°C, energy ranged from Jc 77 2100 J/m2 depending planes Nb sapphire. Greater toughnesses derived bonding 1300°C, owing less oxygen contamination Nb. Interfacial doping by Ag atoms leads a strong reduction only 0.2 0.5 monolayer. Higher is caused greater deformation as observed slip lines metal surface. Evaluation loading characteristics revealed that sharp precursor cracks developed initially ceramic. Extensive crack blunting also occurs, especially bicrystals, but often followed erratic or unstable extension during which far plasticity apparently rate sensitivity deformation.

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