Superplastic behavior of PM SiCp/6061 aluminum alloy composites at high strain rates |
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Authors: | W J Kim Y S Lee C W An |
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Affiliation: | (1) Department of Materials Science and Engineering, Hong-ik University, 72-1 Sangsu-dong, Mapo-ku, 121-791 Seoul, Korea |
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Abstract: | The superplastic behavior of a powder-metallurgy processed 6061 Al composite was investigated as a function of SiC content
increasing from 0% to 30% at 10% increments over a wide temperature range from 430°C to 610°C. The materials were found to
be high-strain-rate superplastic. In the temperature range where grain boundary sliding (GBS) controlled the plastic flow,
the strength of the composite was lower than that of the unreinforced matrix alloy even after compensating for grain size
and threshold stress. This “particle weakening” was in contrast with the particle strengthening observed in the low temperature
range where dislocation climb creep was found to control the plastic flow. In the GBS regime, the strength differential between
the materials was a function of SiC content and temperature, which increased with the increase in SiC content and temperature.
Strong Mg segregation was detected at interfaces between SiC and Al phases in the composites. Evidence for interfacial reaction
reported in the Si3N4 reinforced 6061 Al composites could not be detected in the current composites. Extensive formation of whisker-like fibers
was observed at the fractured surface of the tensile samples above the critical temperature where particle weakening begins
to be exhibited. This result suggests the possibility that partial melting in the solute-enriched region near SiC interfaces
is responsible for the particle weakening in the SiC reinforced 6061 Al composite. |
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Keywords: | composite interface superplastic powder metallurgy particle weakening |
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