Dislocation-grain boundary interactions in Ni sub 3 Al; Effects of structure and chemistry

Journal Article · Sat Jun 01 04:00:00 EDT 1991 · Scripta Metallurgica; (United States)

OSTI ID:5579553

Lee, T C; Subramanian, R; Robertson, I M; Birnbaum, H K ^[1]

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1. Illinois Univ., Urbana, IL (United States). Materials Research Lab.

This paper reports that one of the critical issues in developing an understanding of the response of Ni{sub 3}Al to stress is the interaction between dislocations and grain boundaries. Even in simple metals this issue is complex, depending as it does on the nature and orientation of the grain boundary and the character of the interacting dislocations. In the case of intermetallic alloys, the issue is even more complex, as the additional factors of grain boundary chemistry, local order, etc. play an important role. This si clearly illustrated in the specific case of Ni{sub 3}Al which exhibits brittle intergranular fracture at low temperatures, except for hypo-stoichiometric alloys containing small amounts of Boron. The B-doped alloy exhibits extensive plastic deformation before undergoing ductile rupture. The effect of B is clearly on the response of grain boundaries to the stresses caused by slip dislocations as both ductile and brittle alloys show extensive slip within the grains prior to fracture. Two mechanism have been proposed to account for this effect of B on the fracture process. In one, it is postulated that B segregation to the grain boundaries increases the cohesive energy of the grain boundaries to the extent that stress concentrations at the boundaries are relieved by initiation of slip rather than fracture. This is consistent with the thermodynamic treatment of fracture as it has been observed that B does segregate more strongly to grain boundaries than to external surfaces.

• DOE Contract Number: AC02-76ER01198
• OSTI ID: 5579553
• Journal Information: Scripta Metallurgica; (United States), Journal Name: Scripta Metallurgica; (United States) Vol. 25:6; ISSN 0036-9748; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
360104 -- Metals & Alloys-- Physical Properties
ALLOYS
ALUMINIUM ALLOYS
BRITTLE-DUCTILE TRANSITIONS
CHEMICAL REACTION KINETICS
CRYSTAL STRUCTURE
DISLOCATION PINNING
FABRICATION
FLUID FLOW
FRACTURE PROPERTIES
GAS FLOW
GRAIN BOUNDARIES
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HEAT TREATMENTS
KINETICS
MATERIALS
MATERIALS WORKING
MECHANICAL PROPERTIES
MICROSTRUCTURE
NICKEL ALLOYS
NICKEL BASE ALLOYS
ORDER-DISORDER TRANSFORMATIONS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
REACTION KINETICS
SLIP FLOW
STOICHIOMETRY
THERMODYNAMIC PROPERTIES
THERMOMECHANICAL TREATMENTS