Densification and Mechanical Properties of Nanocrystalline FeAl
Arnett, Michael D.
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https://hdl.handle.net/2142/82921
Description
Title
Densification and Mechanical Properties of Nanocrystalline FeAl
Author(s)
Arnett, Michael D.
Issue Date
1999
Doctoral Committee Chair(s)
Averback, Robert S.
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Metallurgy
Language
eng
Abstract
Impression creep measurements were performed on nanocrystalline FeAl specimens sinterforged to full density. The tests were conducted over the temperature range of 500--600°C, and using punches with diameters of 0.5 and 0.2 mm. For specimens sinterforged at 500°C, a decrease in creep rate was observed between 500°C and 525°C, similar to the decrease in deformation rate observed in sinterforging experiments. The stress exponent was calculated from the steady-state impression velocities at punching stresses of 400, 600 and 800 MPa, which are equivalent to conventional stresses of 130, 195 and 260MPa. The stress exponent was 2 at all temperatures; its value is attributed to a deformation mechanism of grain boundary sliding. The discrepancy between the stress exponent in sinterforging and impression creep tests is attributed to the lower stresses employed in the impression creep experiments, suggesting different mechanisms are presumably in operation in the two regimes. The activation energy for impression creep was 1.6 eV, which is explained by accommodation by grain boundary diffusion. Impression creep tests on nanocrystalline Fe produced similar results; the stress exponent was 2 and the activation energy, 0.8 eV, was indicative of grain boundary diffusion.
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