Kinetics of grain growth in the weld heat-affected zone of Alloy 718
- Oak Ridge National Lab., TN (United States)
- Univ. of Alabama, Birmingham, AL (United States). Dept. of Materials Science an Engineering
Grain-boundary liquation occurs in the weld heat-affected zone (HAZ) of the Ni-base superalloy 718 at locations where the peak temperatures are greater than about 1,200 C. The evolution of the grain structure at the HAZ locations depends upon the interaction between the grains and the grain-boundary liquid. The evolution of grain structure in the presence of grain-boundary liquid was simulated by subjecting samples to controlled thermal cycles using resistance heating. A measurement of grain size as a function of isothermal hold at two peak temperatures of 1,200 C and 1,227 C indicated that in alloy 718, the kinetics of grain growth depended upon the prior thermal history of the alloy. In the solution-treated alloy, the presence of grain-boundary liquid did not arrest grain growth at either peak temperature. In the homogenized and aged alloy, a grain refinement was observed at the peak temperature of 1,227 C, while an arrest of grain growth was observed at a peak temperature of 1,200 C. Liquid film migration (LFM) and subgrain coalescence, either acting alone or simultaneously, are shown to explain most of the observed microstructural phenomena and the kinetics of grain growth in the alloy.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 142326
- Journal Information:
- Metallurgical Transactions, A, Vol. 24A, Issue 12; Other Information: PBD: Dec 1993
- Country of Publication:
- United States
- Language:
- English
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