The thermodynamic driving force for rafting in superalloys

Journal Article · Thu Aug 01 04:00:00 EDT 1996 · Acta Materialia

DOI:https://doi.org/10.1016/1359-6454(95)00423-8· OSTI ID:367326

Nabarro, F R.N.; Cress, C M ^[1]; Kotschy, ^[1]

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1. CSIR, Pretoria (South Africa). Div. of Materials Science and Technology

Eshelby`s energy-momentum tensor is used to provide an analytical expression for the driving force for rafting in the elastic regime in a superalloy with a high volume fraction of {gamma}{prime}. The structure is modelled as a simple cubic array of {gamma}{prime} cubes separated by thin sheets of {gamma}. During rafting, the {gamma}{prime} particles are constrained to remain tetragonal prisms. For tension along a cube axis, the driving force is proportional to the product of the tension {sigma}, the fractional difference {delta} of lattice parameters of {gamma}{prime} and {gamma} and the fractional difference m of their elastic constants c{sub 11} {minus} c{sub 12}. As in the calculation of Pineau for an isolated spheroid, needles are formed when this product {sigma}{delta}m is positive. Two- and three-dimensional systems behave similarly. The initial plastic strain in {gamma} is anelastic and in principle reversible. When the plastic strain exceeds m{delta}, platelets perpendicular to the stress axis are formed if the product {sigma}{delta} is negative.

• OSTI ID: 367326
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 8 Vol. 44; ISSN XZ504Y; ISSN 1359-6454
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DEFORMATION
DISLOCATIONS
ELASTICITY
HEAT RESISTING ALLOYS
LATTICE PARAMETERS
MATHEMATICAL MODELS
MICROSTRUCTURE
PARTICULATES
PLASTICITY
STRAINS
STRESSES
THREE-DIMENSIONAL CALCULATIONS
TWO-DIMENSIONAL CALCULATIONS