Deformation and recrystallization behavior during hot working of a coarse-grain,nickel-base superalloy ingot material |
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Authors: | S L Semiatin D S Weaver R C Kramb P N Fagin M G Glavicic R L Goetz N D Frey M M Antony |
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Affiliation: | (1) the Air Force Research Laboratory, Materials and Manufacturing Directorate, Afrl/Mllm, 45433-7817 Wright-Patterson Air Force Base, OH;(2) Chemical Engineering Department, the University of Dayton, 45409 Dayton, OH;(3) Mechanical Engineering Department, the University of Dayton, 45409 Dayton, OH;(4) UES, Inc., 45432 Dayton, OH;(5) E.T. Concepts, Inc., 43140 London, OH;(6) Allvac, An Allegheny Technologies Company, 28111-5030 Monroe, NC |
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Abstract: | The deformation and dynamic recrystallization behavior of Waspaloy-ingot material with coarse, columnar grains was established
using isothermal uniaxial and double-cone compression tests. Testing was conducted along different test directions relative
to the columnar-grain microstructure at supersolvus temperatures (1066 °C and 1177 °C) and strain rates (0.005 and 0.1 s−1), which bracket typical ingot-breakdown conditions for the material. The flow behavior of axial samples (i.e., those compressed parallel to the columnar-grain direction) showed an initial strain-hardening transient followed by steady-state
flow. In contrast, the stress-strain curves of samples upset transverse to the columnar grains exhibited a peak stress at low strains, whose magnitude was greater than the steady-state flow stress
of the axial samples, followed by flow softening. The two distinct flow behaviors were explained on the basis of the solidification
texture associated with the starting ingot structure, differences in the kinetics of dynamic recrystallization revealed in
the double-cone tests, and the evolution of deformation and recrystallization textures during hot working. Dynamic recrystallization
kinetics were measurably faster for the transverse samples as well as specimens oriented at ∼45 deg to the forging direction,
an effect partially rationalized based on the initial texture and its effect on the input rate of deformation work driving
recrystallization. Despite these differences, the overall strains required for dynamic recrystallization were comparable to
those measured previously for fine-grain (wrought) Waspaloy. However, the Avrami exponents (∼2 to 3) were somewhat higher
than those for wrought material (∼1 to 2), an effect attributable to the particle-stimulated nucleation in the ingot material. |
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