Constitutional liquid film migration in the weld heat affected zone of a nickel-base alloy

Book · Tue Dec 31 04:00:00 EST 1996

OSTI ID:442942

Acoff, V L ^[1]; Thompson, R G ^[2]

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1. Univ. of Alabama, Tuscaloosa, AL (United States)
2. Univ. of Alabama, Birmingham, AL (United States)

It has been discovered that when multiphase alloys are rapidly heated, it is possible to cause melting of the interface between phases. This phenomenon was discovered to exist in the weld heat-affected zone (HAZ) of several alloys and is called constitutional liquation. Constitutional liquation occurs if during melting, the bulk composition is in a non-liquid region of the phase diagram but the tie-line between the liquating phases passes through a liquid region. The liquid produced during constitutional liquation can spread along grain boundaries and promote constitutional liquid film migration (CLFM). Nickel-base alloy 718 has been studied to determine the effect that HAZ peak temperature has on supersaturated solute concentration in the areas behind CLFM grain boundaries. In order to promote CLFM, a Gleeble 1000 thermomechanical device was used to subject heat treated rods of alloy 718 to rapid thermal cycles. Results show that the concentration of niobium in the migrated region (area behind the migrated boundary) was higher than the niobium concentration in the matrix for HAZ peak temperatures below the solidus temperature (1,227 C and 1,240 C). For an HAZ peak temperature above the solidus temperature (1,250 C), there was no significant difference between the niobium concentration in the migrated region and the matrix.

• OSTI ID: 442942
• Report Number(s): CONF-950682--; ISBN 0-87170-567-2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CONCENTRATION RATIO
EXPERIMENTAL DATA
GRAIN BOUNDARIES
HEAT AFFECTED ZONE
INCONEL 718
MELTING
MICROSTRUCTURE
SIMULATION
SOLID SOLUTIONS
WELDED JOINTS