Effects of mushy zone tensile stresses on pore nucleation in superalloy 718
- Auburn Univ., AL (United States)
Inadequate feeding of shrinkage during solidification can impose large tensile stresses upon the mushy zone of a casting. These stresses can be relieved by (1) plastic deformation of the dendritic network and/or (2) nucleation of pores in the interdendritic liquid. Analogous to other nucleation processes, heterogeneous nucleation of micropores at non-wetting inclusions in the liquid is expected to be thermodynamically favored over either plastic deformation of the solid or homogeneous nucleation of micropores in the liquid. The stress-induced nucleation of pores in liquid metals is examined in the present paper using a thermodynamic model and compared with experimental mushy-zone tensile data of superalloy 718. The thermodynamic model predicts that a threshold stress should be exceeded before pores are nucleated at a substantial rate. Mushy zone tension tests were performed on superalloy 718 under constant strain rates of 0.0014/sec, 0.0026/sec, and 0.0046/sec. Increasing amounts of liquid in the mushy zone significantly reduced the total failure strain. Interrupted tests showed that the fracture of the experimental samples occurred by a pore nucleation, growth, and coalescence mechanism. The highest strain rates caused sample failure with very low levels of strain, presumably due to stress concentration effects from inhomogeneous deformation.
- OSTI ID:
- 428087
- Report Number(s):
- CONF-960815-; ISBN 0-7918-1505-6; TRN: IM9708%%416
- Resource Relation:
- Conference: 31. national heat transfer conference, Houston, TX (United States), 3-6 Aug 1996; Other Information: PBD: 1996; Related Information: Is Part Of ASME proceedings of the 31. national heat transfer conference: Volume 1. HTD-Volume 323; Prasad, V. [ed.] [State Univ. of New York, Stony Brook, NY (United States)]; Bergman, T.L. [ed.] [Univ. of Texas, Austin, TX (United States)]; Thynell, S.T. [ed.] [Pennsylvania State Univ., University Park, PA (United States)] [and others]; PB: 321 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
A crystal plasticity model incorporating the effects of precipitates in superalloys: Application to tensile, compressive, and cyclic deformation of Inconel 718
Tensile mechanical properties and fracture behaviors of nickel-based superalloy 718 in the presence of hydrogen