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Metallurgical Transactions A

, Volume 23, Issue 6, pp 1737–1750 | Cite as

An investigation of the effects of microstructure on the fatigue and fracture behavior of α2 + β forged Ti-24Al-11Nbforged Ti-24Al-11Nb

  • W. O. Soboyejo
Mechanical Behavior

Abstract

The results of a recent study of the effects of Widmanstätten and basket weave microstructures on the fracture toughness and fatigue crack growth behavior of Ti-24Al-11 Nb are reported Intrinsic and extrinsic toughening components due to crack blunting and bridging by the β phase, crack deflection, and microcracking are computed from existing crack-tip shielding models. Predictions of fracture toughness and fatigue thresholds obtained by the superposition of extrinsic toughening components are compared with measured values obtained from compression precraked single edge notch (SEN) bend specimens. The results indicate that the continuity of the β matrix between the α2 laths is important for the effectiveness of crack-tip blunting mechanisms. Widmanstätten microstructures obtained by annealing solely in the α2 + β phase field are shown to promote crack deflection and unstable room-temperature fatigue crack growth rates.i.e., crack growth rates that increase after further thermal exposure in the α2 + β and field. Basket weave microstructures produced by two-stage annealing (TSA) in the β and α2 + β phase fields are shown to promote crack bifurcation and deflection and significant improvements in fatigue crack growth resistance when the β anneal is followed by a furnacecool. The article highlights the significant role of microcracking in the fatigue propagation mechanism. The micromechanisms of fatigue and fracture are also discussed for the microstructures examined.

Keywords

Fracture Toughness Crack Growth Rate Fatigue Crack Growth Phase Field Fatigue Crack Growth Rate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 1992

Authors and Affiliations

  • W. O. Soboyejo

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