The intergranular segregation of boron in substoichiometric Ni/sub 3/Al

Technical Report · Tue Dec 01 04:00:00 EST 1987

DOI:https://doi.org/10.2172/5683643· OSTI ID:5683643

Choudhury, A.

The intermetallic compound Ni/sub 3/Al offers promise as a material for high temperature applications. In addition to its unusual property of increasing strength with temperature (until approx.700/sup 0/C), it has excellent corrosion and oxidation resistance. Microalloying the alloy with boron has been shown to be dramatically effective in improving its inherent intergranular brittleness. This improvement results from the strong tendency of boron to segregate to the grain boundaries of Ni/sub 3/Al. This research deals with the study of the segregation behavior of boron. Auger electron spectroscopy was chosen as the technique adopted to study this segregation. The strong effect of segregant level on the grain boundary strength level can be controlled by thermal history variations and by variations in the level of solute in the bulk. Cathodic hydrogen charging was shown to be a potent tool in opening up other wise cohesive boundaries for analysis. The effective binding energy of boron at the grain boundaries of Ni/sub 3/Al was calculated from experimental data; it was found to vary between 0.2 and 0.45 eV. Kinetics of segregation have been investigated; the present set of kinetic studies were shown to be inadequate to find a diffusion coefficient and that temperatures lower than those studied here need to be used. As an associated investigation, a set of elemental standards were developed for the particular scanning Auger microprobe used in this study. 141 refs., 94 figs., 26 tabs.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5683643
• Report Number(s): ORNL/TM-10508; ON: DE88004783
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ALLOYS
ALUMINIUM ALLOYS
AUGER ELECTRON SPECTROSCOPY
BINDING ENERGY
BORON
BORON ADDITIONS
BORON ALLOYS
BRITTLENESS
CHEMICAL COMPOSITION
COOLING
CORROSION RESISTANCE
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DIFFUSION
DISLOCATIONS
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY
EQUATIONS
FRACTOGRAPHY
GRAIN BOUNDARIES
HEAT TREATMENTS
INTERMETALLIC COMPOUNDS
INTERSTITIALS
KINETICS
LATTICE PARAMETERS
LINE DEFECTS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NICKEL ALLOYS
NICKEL BASE ALLOYS
POINT DEFECTS
SEGREGATION
SEMIMETALS
SPECTROSCOPY
TEMPERATURE EFFECTS
YIELD STRENGTH