| Summary: | 碩士 === 國立臺灣大學 === 機械工程學系 === 86 === The three kind of aluminum alloys in common use,Al2024
-T351,Al6061-T6 and Al7075-T6,are adopted as the specimen
materials. We operated an uniaxial-stress compression test
on the Material Testing System at temperatures of 18 to
300℃ and at average true-strain-rates of 100 to 500s-1.
It is a high-strain-rate experiment.
The trends of flow stress curves depend on effects of
work-hardening and work-softening. In this experiment,high
strain rates and short deformation time result in that a
great quantity of heat transformed from plastic work is
unable to radiate,and then temperature increase happens in
the specimen. Therefore the effects of dynamic recovery are
enhanced. The results of the experiment show that,
strain-hardening happens after yielding at low temperature,
but the effects of dynamic recovery cause that the flow
stress curves roughly show a level at last. With the increase
of temperature,strain-hardening becomes less serious and the
flow stress curves become decendant.
In the temperature range of much lower and higher than
recrystallization temperature,the effects of temperature are
less important than those of strain rate. In the temperature
range close to recrystallization temperature,the effects of
temperature are as important as those of strain rate and the
change of yield stress is greater.
KEY WORD : dynamic recovery,strain-hardening,recrystallization.
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