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The first half of this work concerns a study on the
feasibility of introducing non-heat-treatable high silicon
aluminum alloy wheel materials to domestic aluminum alloy
wheel foundries. The Al-11% Si alloys containing 0.2 ∼0.3%
Mg were selected as candidates in this study and subjected to a
series of in-lab evaluations and production-line trials. The
results showed that the Al-11% Si-0.2∼0.3% Mg Alloy
specimens can be best modified through an ad- dition of
0.03% Sr which gave rise to a modification rating of class
4∼5. A water quench procedure of the castings right after
their removal from mould was found beneficial to the
mechanical properties. In comparison with the Sr- modified
specimens, the Al-11% Si-0.2∼0.3% Mg alloys modified by
0.16∼0.32% Sb exhibit poor modification rating with aspect
ratios of eutectic silicon rating from 14:1∼6:1. Analysis
of trial-cast Sr-modified high-silicon Al alloy wheels shows
satisfactory microstructural characteristics with tensile
strength , elongation and quality index of 184 MPa, 4.8%
and 286MPa, respectivety, which were similar to those
obtained from imported commerical non-heat- treatable high-
silicon aluminum alloy wheels.
The second half of this aims to investigate the effects of
wetting pro- moters Ca and Mg and the modifier Sr on the
Al-11% Si-0.3% Mg/SiCp composites. The microstructures of the
composite and the interphases at reinforcing par- ticles/Al
alloy matrix interfaces of the composites were investigated by
OM, SEM/EDAX and XRD. Mechanical properties of the
composites were examined by tensile tests and bending test.
The results showed that the bonding strength of SiC
particulate to the aluminum alloy matrix can be greatly
enhanced by the wetting prometer Ca and that the modifier
Sr helps to produce desirable silicon morphology in aluminum
alloy matrix for improved properties.
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