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Title: Structure, chemistry and bonding at grain boundaries in Ni{sub 3}Al. 1: The role of boron in ductilizing grain boundaries

Abstract

Boron segregation is known to change the fracture mode from intergranular to transgranular in Ni-rich Ni{sub 3}Al. This paper addresses the question of why boron segregation at grain boundaries improves their resistance to fracture. Grain boundaries in B-free and B-doped Ni-rich Ni{sub 3}Al (76 at.% Ni) were examined using spatially resolved electron energy loss spectroscopy (EELS), energy dispersive X-ray spectroscopy (EDS) and annular dark field (ADF) imaging in an UHV scanning transmission electron microscope, as well as conventional electron microscopy techniques. Ni-enrichment was seen in a 0.5--1.0 nm wide region at large angle boundaries, both in the absence and presence of B. using EELS, B segregation to the boundary was observed to vary along the interface. EELS of the Ni L{sub 2.3} edge showed that the B-rich regions have a bonding similar to that in bulk Ni{sub 3}Al, while the B-free regions have a bonding similar to the more Ni-like character of undoped boundaries. These results demonstrate that boron segregation increases the cohesive strength of grain boundaries in Ni{sub 3}Al by making the bonding at the boundary similar to that in the bulk and, in this manner, increases their fracture resistance.

Authors:
; ; ;  [1];  [2]
  1. Cornell Univ., Ithaca, NY (United States)
  2. IBM Thomas J Watson Research Center, Yorktown Heights, NY (United States)
Publication Date:
OSTI Identifier:
230801
DOE Contract Number:  
FG02-85ER45211; FG02-87ER45322
Resource Type:
Journal Article
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 44; Journal Issue: 4; Other Information: PBD: Apr 1996
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; NICKEL ALLOYS; GRAIN BOUNDARIES; FRACTURE PROPERTIES; ALUMINIUM ALLOYS; BORON; METALLURGICAL EFFECTS; INTERMETALLIC COMPOUNDS; SEGREGATION; ENERGY-LOSS SPECTROSCOPY; X-RAY SPECTROSCOPY; TRANSMISSION ELECTRON MICROSCOPY; CHEMICAL COMPOSITION; BONDING

Citation Formats

Muller, D A, Subramanian, S, Sass, S L, Silcox, J, and Batson, P E. Structure, chemistry and bonding at grain boundaries in Ni{sub 3}Al. 1: The role of boron in ductilizing grain boundaries. United States: N. p., 1996. Web. doi:10.1016/1359-6454(95)00267-7.
Muller, D A, Subramanian, S, Sass, S L, Silcox, J, & Batson, P E. Structure, chemistry and bonding at grain boundaries in Ni{sub 3}Al. 1: The role of boron in ductilizing grain boundaries. United States. doi:10.1016/1359-6454(95)00267-7.
Muller, D A, Subramanian, S, Sass, S L, Silcox, J, and Batson, P E. Mon . "Structure, chemistry and bonding at grain boundaries in Ni{sub 3}Al. 1: The role of boron in ductilizing grain boundaries". United States. doi:10.1016/1359-6454(95)00267-7.
@article{osti_230801,
title = {Structure, chemistry and bonding at grain boundaries in Ni{sub 3}Al. 1: The role of boron in ductilizing grain boundaries},
author = {Muller, D A and Subramanian, S and Sass, S L and Silcox, J and Batson, P E},
abstractNote = {Boron segregation is known to change the fracture mode from intergranular to transgranular in Ni-rich Ni{sub 3}Al. This paper addresses the question of why boron segregation at grain boundaries improves their resistance to fracture. Grain boundaries in B-free and B-doped Ni-rich Ni{sub 3}Al (76 at.% Ni) were examined using spatially resolved electron energy loss spectroscopy (EELS), energy dispersive X-ray spectroscopy (EDS) and annular dark field (ADF) imaging in an UHV scanning transmission electron microscope, as well as conventional electron microscopy techniques. Ni-enrichment was seen in a 0.5--1.0 nm wide region at large angle boundaries, both in the absence and presence of B. using EELS, B segregation to the boundary was observed to vary along the interface. EELS of the Ni L{sub 2.3} edge showed that the B-rich regions have a bonding similar to that in bulk Ni{sub 3}Al, while the B-free regions have a bonding similar to the more Ni-like character of undoped boundaries. These results demonstrate that boron segregation increases the cohesive strength of grain boundaries in Ni{sub 3}Al by making the bonding at the boundary similar to that in the bulk and, in this manner, increases their fracture resistance.},
doi = {10.1016/1359-6454(95)00267-7},
journal = {Acta Materialia},
number = 4,
volume = 44,
place = {United States},
year = {1996},
month = {4}
}