Abstract
Alloy 718 suffers from microfissuring in the weld heat-affected zone, and compositional, structural and mechanistic causes of this defect have been examined. Both bulk sulfur and bulk carbon increase microfissuring, and heat treatments typical ofhomogenization, solution annealing and age hardening reveal that microfissuring is sensitive to the microstructural and chemical distributions established during heat treatment. Increased grain size increases microfissuring more than heat treatment or bulk chemistry. The mechanistic cause of microfissuring, constitutional liquation of niobium carbide and Laves phases, produces intergranular liquid films with wetting angles that are dependent on the chemical composition of the grain boundary region prior to welding. Microfissuring also correlates with the temperature dependence of the intergranular liquid wetting angle in the heat-affected zone.
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Additional information
R.G. Thompson received his Ph. D. in materials science and engineering from Vanderbilt University. He is currently an associate professor in the Department of Materials Engineering at the University of Alabama at Birmingham. Dr. Thompson is also a member of TMS.
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Thompson, R.G. Microfissuring of Alloy 718 in the Weld Heat-Affected Zone. JOM 40, 44–48 (1988). https://doi.org/10.1007/BF03258151
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DOI: https://doi.org/10.1007/BF03258151