In-situtransmission electron microscopy study of dislocation processes at precipitate-free zones in aγ′-strengthened superalloy
- 1 December 2003
- journal article
- research article
- Published by Taylor & Francis in Philosophical Magazine
- Vol. 83 (35), 4011-4029
- https://doi.org/10.1080/14786430310001603445
Abstract
In precipitation-strengthened polycrystals, precipitate-free zones (PFZs) often form along grain boundaries. These PFZs lower the yield strength. In this investigation, thin foils of the commercial γ′-strengthened nickel-based superalloy Nimonic PE16 have been strained inside a transmission electron microscope and the relevant dislocation processes in the PFZs and in the γ′-strengthened material next to them have been observed under load. Since the PFZs are only solid solution strengthened, they are softer than the interior of the γ′-strengthened grains. Many different slip systems are activated in the PFZs even at relatively low external stresses. Multiple slip allows for compatible deformation of neighbouring grains. Extensive cross-slip and double cross-slip in the PFZs lead to a high dislocation multiplication rate. Easy creation of dislocations in the PFZs and pile-ups at the border between the PFZs and the γ′-strengthened interior of the grains enhance the propagation of slip across grain boundaries and thus lower the yield strength of the material.Keywords
This publication has 32 references indexed in Scilit:
- Quantification of the detrimental effects of precipitate free zones on the yield strength of a superalloyScripta Materialia, 2003
- The effects of precipitation free zones on order strengthening in NIMONIC PE16 bi-crystalsMaterials Science and Engineering: A, 2001
- Local order in industrial and model γ phases of superalloysActa Materialia, 2001
- Low cycle fatigue of a nickel based superalloy at high temperature: deformation microstructuresMaterials Science and Engineering: A, 2001
- The effect of chromium on the solubility limits of the γ′-forming elements in a NiFeCr base superalloyScripta Metallurgica et Materialia, 1994
- Slip-plane disordering in stoichiometric Ni3AlPhilosophical Magazine A, 1991
- Determination of the local tensile axis direction in a tem in situ strained γ′ single crystal—a finite element approachActa Metallurgica et Materialia, 1990
- Stiffness constants, dislocation line energies, and tensions of Ni3Al and of the γ′-phases of NIMONIC 105 and of NIMONIC PE16Physica Status Solidi (a), 1987
- Precipitation hardening of superalloys by ordered γ′-particlesProgress in Materials Science, 1985
- The effects of elastic anisotropy on dislocation line tension in metalsJournal of Physics F: Metal Physics, 1972