On the nature of lattice distortion near the {gamma}/{gamma}{prime} interfaces in nickel-base superalloys

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(97)00033-X· OSTI ID:509154

Mukherji, D; Wahi, R P ^[1]

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1. Hahn-Meitner-Inst. GmbH, Berlin (Germany)

Nickel base superalloys are strengthened by ordered {gamma}{prime} precipitates of L1{sub 2} structure, which are coherently embedded in the {gamma} matrix (fcc). The precipitate and the matrix are in a cube/cube orientation relationship. The mismatch in lattice parameter ({delta}) between the two phases influences the mechanical properties of these alloys. The value and the sign of {delta} also control the morphological changes in {gamma}{prime} (rafting), which occur during deformation at high temperatures and at low strain rates. In designing these superalloys, the mismatch can be controlled through a modification of the composition. For these reasons measurement of {delta} is important in order to understand the alloy behavior. Several experimental techniques have been used for the measurement of {delta} which include X-ray diffraction (XRD), neutron diffraction (ND) and convergent beam electron diffraction (CBED). In the present paper the authors present results from CBED measurements in [014] zone axis to show that the distortion is not only tetragonal, there is also angular distortion in the unit cell in addition to the dilation/contraction in some of the lattice dimensions. The experimental results are verified on the basis of computer simulations of the HOLZ patterns from crystals subjected to different distortions. A geometrical model of the lattice across the {gamma}/{gamma}{prime} interface is also presented.

• OSTI ID: 509154
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 11 Vol. 36; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CHROMIUM ALLOYS
COMPUTERIZED SIMULATION
INTERFACES
LATTICE PARAMETERS
MICROSTRUCTURE
MOLYBDENUM ALLOYS
NICKEL BASE ALLOYS
PARTICLE SIZE
PRECIPITATION
TANTALUM ALLOYS
TITANIUM ALLOYS