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Micromechanisms of Deformation and Fracture in Rapidly Solidified Ni3Al Alloys

Published online by Cambridge University Press:  26 February 2011

G. Liu
Affiliation:
Department of Materials and Metallurgical Engineering, New Mexico Tech, Socorro, New Mexico 87801
G.M. Bond
Affiliation:
Department of Materials and Metallurgical Engineering, New Mexico Tech, Socorro, New Mexico 87801
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Abstract

Rapidly solidified Ni76 Al24 ribbons, with and without boron, have been the subject of in-situ TEM deformation studies, as well as X-ray and TEM characterization and TEM fractography. The aim has been to gain a better understanding of the influence of a reduced degree of order on grainboundary behavior and ductility. This, in turn, allows fresh insights to be gained, both into the manner in which boron additions can enhance ductility, and into the potential usefulness of sequential ordering in intermetallic alloys with a tendency to intergranular failure. Lower degrees of order are found to reduce stress concentrations at grain boundaries; this effect is due to easier generation of dislocations from boundary sources, and, to a lesser extent, the braking action of thermal APB's on dislocation motion. The beneficial effect of boron on ductility is seen to result, at least in part, from enhanced boundary cohesive strength.

Type
Research Article
Copyright
Copyright © Materials Research Society 1991

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