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The effect of adding magnesium on the aging behavior of Al-Zn-
Mg alloy reinforced with aluminum (Al2O3) was studied using
differential scanning calorimeter(DSC) technique, hardness
measurement. The magnesium contents were varied from 1.23wt% to
2.97wt%. The addition of magnesium was found to increase the
amount of η'-phase formation in composites. The formation
enthalpy of composites was 0.932cal/g and 1.375cal/g for lower
magne- sium content(1.23wt%) and higher magnesium content(2.97
wt%) respectively. The time needed for the saturation of
precipiat- ing in the composites changed from 12 hr to 48hr as
the magne- sium content increased from 1.23wt% to 2.97wt%. The
maximum hardness occurred in composites with 2.97wt% Mg that
contained a maximum amounts of η'-phase precipitates. The
hardness of the composites was always less than that of monoli-
thic alloys because of alumina fibers caused suppression of η'
formation in composites. Difference of wearability between
composites and Al-Zn-Mg alloy was also performed in this study.
The weight loss decreased with increasing the volume fraction
of alumina and with increasing the magnesium content.
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