The influence of interface impurities on fracture energy of UHV diffusion bonded metal-ceramic bicrystals

Elssner, G.; Korn, D.; Rühle, M.

doi:10.1016/0956-716x(94)90523-1

Cited by 149 publications

(100 citation statements)

References 5 publications

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“…When foils with sulphur segregant were used to prepare bonds, segregation at the niobium/sapphire interface was negligible, and changes in G c were small (within experimental error). In contrast, titanium substantially increases G c ; increased interfacial adhesion increases the contribution of plasticity to the work of fracture [48].…”

Section: Role Of Interfacial Impuritiesmentioning

confidence: 99%

“…Thus, impurities that segregate to this interface can affect the resulting fracture strength directly through their effect on interfacial adhesion, and indirectly through the effect of adhesion on plastic dissipation accompanying fracture. Korn et al [35] and Elssner et al [48] examined the influence of interface impurities (Ag, S, Ti) on the fracture energy of uhv bonded niobium/sapphire bicrystals prepared at 1400°C.…”

Section: Role Of Interfacial Impuritiesmentioning

confidence: 99%

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Joining of alumina via copper/niobium/copper interlayers

et al. 2000

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Alumina has been joined at 1150°C and 1400°C using multilayer copper/niobium/copper interlayers. Four-point bend strengths are sensitive to processing temperature, bonding pressure, and furnace environment (ambient oxygen partial pressure). Under optimum conditions, joints with reproducibly high room temperature strengths (≈240 ± 20 MPa) can be produced; most failures occur within the ceramic. Joints made with sapphire show that during bonding an initially continuous copper film undergoes a morphological instability, resulting in the formation of isolated copper-rich droplets/particles at the sapphire/interlayer interface, and extensive regions of direct bonding between sapphire and niobium. For optimized alumina bonds, bend tests at 800°C-1100°C indicate significant strength is retained; even at the highest test temperature, ceramic failure is observed. Postbonding anneals at 1000°C in vacuum or in gettered argon were used to assess joint stability and to probe the effect of ambient oxygen partial pressure on joint characteristics. Annealing in vacuum for up to 200 h causes no significant decrease in room temperature bend strength or change in fracture path. With increasing anneal time in a lower oxygen partial pressure environment, the fracture strength decreases only slightly, but the fracture path shifts from the ceramic to the interface. Cu/Nb/Cu Interlayers R. A. Marks et al. Joining of Alumina via

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Section: Role Of Interfacial Impuritiesmentioning

confidence: 99%

Section: Role Of Interfacial Impuritiesmentioning

confidence: 99%

Joining of alumina via copper/niobium/copper interlayers

et al. 2000

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“…It does not explain how cracks are able to propagate quasi-statically when atomic separation is the fracture mechanism. Recent experiments on metalceramic interfaces (Elssner et al, 1994;Bagchi et al, 1994;Bagchi and Evans, 1996) have provided detailed evidence of quasi-static propagation of interface decohesion cracks in the presence of substantial plasticity in the metal. Another approach, pursued most recently by Suo et al (1993) and Beltz, et al (1996), employs a model which excludes plasticity within some distance D from the crack tip.…”

Section: Introductionmentioning

confidence: 99%

Steady-state crack growth and work of fracture for solids characterized by strain gradient plasticity

Wei

Hutchinson

1997

Journal of the Mechanics and Physics of Solids

263

205

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Mode I steady-state crack growth is analysed under plane strain conditions in small scale yielding. The elastic-plastic solid is characterized by a generalization of JZ flow theory which accounts for the influence of the gradients of plastic strains on hardening. The constitutive model involves one new parameter, a material length 1, specifying the scale of nonuniform deformation at which hardening elevation owing to strain gradients becomes important. Gradients of plastic strain at a sharp crack tip result in a substantial increase in tractions ahead of the tip. This has important consequences for crack growth in materials that fail by decohesion or cleavage at the atomic scale. The new constitutive law is used in conjunction with a model which represents the fracture process by an embedded traction-separation relation applied on the plane ahead of the crack tip. The ratio of the macroscopic work of fracture to the work of the fracture process is calculated as a function of the parameters characterizing the fracture process and the solid, with particular emphasis on the role of 1. 0 1997 Elsevier Science Ltd

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“…Results can be compared to fracture toughness behavior that has been reported for a variety of niobium/alumina samples prepared by conventional diffusion bonding methods, for which the interfacial chemistry and other factors may differ. [12][13][14][15][16][17][18][19] …”

Section: Introductionmentioning

confidence: 99%

Fracture and Fatigue Behavior at Ambient and Elevated Temperatures of Alumina Bonded with Copper/Niobium/Copper Interlayers

Kruzic

Marks

Yoshiya

et al. 2002

Journal of the American Ceramic Society

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Interfacial fracture toughness and cyclic fatigue-crack growth properties of joints made from 99.5% pure alumina partial transient-liquid phase bonded using copper/niobium/copper interlayers have been investigated at both room and elevated temperatures, and assessed in terms of interfacial chemistry and microstructure. The mean interfacial fracture toughness, G c , was found to decrease from 39 to 21 J/m 2 as temperature was raised from 25° to 1000°C, with failure primarily at the alumina/niobium interfaces. At room temperature, cyclic fatigue-crack propagation occurred at both the niobium/alumina interface and in the alumina adjacent to the interface, with the fatigue threshold, ∆G TH , ranging from 20 -30 J/m 2 ; the higher threshold values in that range resulted from a predominantly near-interfacial (alumina) crack path. During both fracture and fatigue failure, residual copper at the interface deformed and remained adhered to both sides of the fracture surface, acting as a ductile second phase, while separation of the niobium/alumina interface appeared relatively brittle in both cases. The observed fracture and fatigue behavior is considered in terms of the respective roles of the presence of ductile copper regions at the interface which provide toughening, extrinsic toughening due to grain bridging during crack propagation in the alumina, and the relative crack propagation resistance of each crack path, including the effects of segregation at the interfaces found by Auger spectroscopy.

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The influence of interface impurities on fracture energy of UHV diffusion bonded metal-ceramic bicrystals

Cited by 149 publications

References 5 publications

Joining of alumina via copper/niobium/copper interlayers

Joining of alumina via copper/niobium/copper interlayers

Steady-state crack growth and work of fracture for solids characterized by strain gradient plasticity

Fracture and Fatigue Behavior at Ambient and Elevated Temperatures of Alumina Bonded with Copper/Niobium/Copper Interlayers

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