Al-17Si-4.5Cu-0.5Mg-(0-6)Fe-(0-2)Mm
(Mm: misch metal) rapidly solidified powder metallurgy
(RSP) alloys were prepared by the hot extrusion
method. Effects of the testing temperature, the
Si particle size, the Fe content and the misch-metal
addition on the high temperature tensile property
and deformation behavior of these alloys were
investigated. In Al-17Si-4.5Cu-0.5Mg alloys, the
superplastic behavior was observed at 500°C
with an initial strain rate of 10-2s-1.
At 520°C, superplasticity
was obtained at an initial strain rate 10-1s-1
which is higher than the case at 500°C.
The tensile elongation by superplasticity increased
with decreasing Si particle size, but superplasticity
was obtained at the same strain rate. With increasing
Fe content, the average matrix grain size decreased
and the superplastic strain rate increased, but
the maximum tensile elongation decreased. The
misch-metal addition has a significant effect
of retardation coarsening of matrix grains by
homogeneous precipitation particles, and superplasticity
was obtained at a high strain rate of 100s-1.
It is concluded that the superplastic elongation
of Al-Si RSP alloys is affected by the size of
dispersing particulates.
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