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The Influence of Mobile Dislocation Density on the Fracture Toughness of B2-Based Ni-Fe-Al Alloys

Published online by Cambridge University Press:  15 February 2011

A. Misra ,
R. D. Noebe  and
R. Gibala
A. Misra
Affiliation:
Department of Materials Science and Engineering, The University of Michigan, Ann Arbor, MI 48109 -2136
R. D. Noebe
Affiliation:
NASA Lewis Research Center, Cleveland, OH 44135.
R. Gibala
Affiliation:
Department of Materials Science and Engineering, The University of Michigan, Ann Arbor, MI 48109 -2136
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Abstract

The deformation and fracture behaviors of two directionally solidified multi-phase Ni-Fe-Al ordered alloys were investigated. One alloy consisted of continuous β+γ lamellae with fine γ precipitates within the γ phase. The NiAl-based β phase of this alloy exhibited <100> slip even when deformed parallel to the [001] growth direction. This material exhibited an initiation fracture toughness of ∼ 30 MPa √m and tensile ductility of 10%. The second alloy consisted of aligned but discontinuous γ lamellae within a continuous β phase. Again, the γ phase contained γ precipitates, but unlike the previous alloy, the β phase also contained a fine dispersion of bcc precipitates due to spinodal decomposition. The β phase of this alloy deformed by <111> slip. This four-phase alloy exhibited a fracture toughness of ∼ 21 MPa √m and tensile ductility of 2%. Observations of the plastic zone in both alloys indicated significant plasticity in the β phase due to easy slip transfer from the ductile second phase. The enhanced fracture resistance of these multiphase materials compared to single phase β alloys is attributed in large part to intrinsic toughening of the β phase by an increased mobile dislocation density due to efficient dislocation generation from the β/γ interfaces.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 350: Symposium U – Intermetallic Matrix Composites III , 1994 , 243
Copyright
Copyright © Materials Research Society 1994

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