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The effect of small amounts of magnesium on the superplastic behavior of an aluminum-zinc alloy

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Title The effect of small amounts of magnesium on the superplastic behavior of an aluminum-zinc alloy
Names Abbott, Vaughn William (creator)
Paasche, Olaf G. (advisor)
Date Issued 1967-08-31 (iso8601)
Note Graduation date: 1968
Abstract The base Al-Zn superplastic alloy was investigated at 250°C to
determine the effect of small amounts of magnesium on mechanical
properties. Six alloys of nominal composition 0.00, 0.10, 0.25,
0.50, 0.75, and 1.00 weight percent magnesium, constant 78 weight
percent zinc, and variable 21 to 22 weight percent aluminum were
each tested in tension at strain rates of 0.02, 0.20, and 2.00 in/min
to determine the flow stress and elongation at each strain rate for
each composition.
Superplastic elongation occurred at all three strain rates in
the specimens containing no magnesium. The addition of any magnesium
content investigated destroyed any significant superplastic deformation
and led to intercrystalline fracture of all other test specimens.
The intermetallic compound Mg₂Zn₁₁ was uniformly distributed throughout the microstructure, limiting plastic deformation.
In general, the flow stress was found to increase to a maximum
as the magnesium content was increased up to about 0.75 percent,
then to start dropping off. At the same time, after the initial drop in
elongation due to the change from the superplastic to the intercrystalline
fracture mode, the trend in elongation was to decrease slowly
with increasing magnesium content. For a given magnesium content,
a higher strain rate resulted in a higher value for the flow stress.
Genre Thesis/Dissertation
Topic Aluminum-magnesium-zinc alloys
Identifier http://hdl.handle.net/1957/46985

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