SEDL / STP / STP1360-EB / STP13409S

The Fracture and Fatigue Crack Growth Behavior of Forged Damage-Tolerant Niobium Aluminide Intermetallics

Ye, F
Post-doctoral research associate, The Ohio State University, Columbus, OH

Mercer, C
Post-doctoral research associate, The Ohio State University, Columbus, OH

Farkas, D
Professor, Virginia Polytechnic Institute and State University, Blacksburg, VA

Soboyejo, WO
Professor, Princeton University, Princeton, NJ

Pages: 21    Published: Jan 2000

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Abstract

The micromechanisms of fracture and fatigue crack growth are elucidated for a new class of damage-tolerant niobium aluminide Nb³Al-xTi intermetallics. Fatigue crack growth in alloys containing 10 and 25 at% Ti is shown to occur primarily by cleavage, while alloys containing ∼40 at% Ti are shown to exhibit similar fracture and fatigue crack growth behavior to ductile metals and their alloys. Slower elevated-temperature (750°C) crack growth rates in the Nb³Al-40Ti alloy are attributed largely to the effects of oxide-induced crack closure. The transition from cleavage fracture (in the Nb³Al-10Ti and Nb³Al-25Ti alloys) to ductile fracture in the Nb³Al-40Ti is correlated with the onset of significant levels of crack-tip plasticity, which is predicted using atomistic simulations.