Elevated temperature deformation behavior of a dispersion-strengthened Al-Fe,V,Si alloy |
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Authors: | Shantanu Mitra |
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Affiliation: | (1) the Components Group, Hewlett-Packard Co., 3175 Bowers, 95054 Santa Clara, CA |
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Abstract: | The deformation behavior of a rapidly solidified, dispersion-strengthened Al alloy containing 11.7 pct Fe, 1.2 pct V, and
2.4 pct Si was studied at test temperatures up to 450 °C using constantstress creep and constnt strain-rate tensile tests.
Apparent stress exponents (n) up to ∼24 and an activation energy of 360 kJ/mol were obtained with the standard Arrhenius type power-law creep equation,
which also suggested a change in behavior at ∼300 °C. Substructure-invariant and dislocation/dispersoid interaction models
were found to be inadequate for explaining the behavior. When the data were replotted as
vs σ, two regimes were found between 350 °C and 450 °C. A model with a pseudothreshold stress (σ
Th′
) for the higher stress regime resulted inn ∼3, indicating solute drag in this regime. Transmission electron microscopy (TEM) showed departureside pinning of dislocations
at higher stresses. In the lower stress regime, TEM showed dislocation subgrain structures. Here, the model resulted in a
stress exponent of ∼4.5 indicating the dislocation climb mechanism. At temperatures below ∼300 °C, a single regime was found
along with lower activation energies and a stress dependence of ∼3. Dislocation pipe diffusion is proposed to explain the
lower activation energy. The origin ofσ
Th′
has been tied to dislocation generation at the grain boundaries. |
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Keywords: | |
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