Intergranular segregation of boron in substoichiometric Ni/sub 3/Al

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:7204140

Choudhury, A

The intermetallic compound Ni/sub 3/Al offers promise as an excellent candidate 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. It has also been observed that 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 first detailed study of the segregation behavior of this beneficial segregant. By virtue of its surface sensitivity, 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 otherwise cohesive boundaries for analysis. At a more fundamental level, the effective binding energy of boron at the grain boundaries of Ni/sub 3/Al was calculated form experimental data; it was found to vary between 0.2 and 0.45 eV. The kinetics of segregation were investigated.

• Research Organization: Tennessee Univ., Knoxville (USA)
• OSTI ID: 7204140
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
ALUMINIUM ALLOYS
AUGER ELECTRON SPECTROSCOPY
BORON ADDITIONS
BORON ALLOYS
CRYSTAL STRUCTURE
ELECTRON SPECTROSCOPY
GRAIN BOUNDARIES
INTERMETALLIC COMPOUNDS
METALLURGICAL EFFECTS
MICROSTRUCTURE
NICKEL ALLOYS
SEGREGATION
SPECTROSCOPY