<p>Aluminum-Silicon (Al-Si) alloys are often preferred in the die casting
industry due to excellent castability, high strength, corrosion resistance and
low cost. Commonly, iron (Fe) is alloyed with the alloys to prevent die
soldering. However, the addition of Fe in most of Al-Si alloys leads to
formation of the intermetallic β-AlFeSi.
The β-AlFeSi is harmful
to the alloy structural integrity due to its needle-like morphology that creates
stress concentration at the microscopic level. The phase presence is
unfavorable to the mechanical properties and significantly reduces the
elongation of the alloys. This research attempted to find viable way to control
the morphology and formation of the β-AlFeSi
phase.</p>
<p>Thermodynamic simulations were done to investigate the sequence of
intermetallic formation and other phases at different alloy compositions. The analysis of solidification
paths of different alloys provided the correlation between the phase formation
sequence and the fraction of the β-AlFeSi phase. The analysis also identified the feasible region of alloy
design for minimizing the β-AlFeSi formation. Based on the thermodynamics simulation analysis, five
alloys of different compositions were designed to validate the finding of the
simulation. </p>
<p>The tensile test
results of the alloys indicated that lowering the Fe content increases the
elongation of the alloy. The results also showed that elongation was reduced with
the increase of Si level due to the formation of eutectic Silicon. The change
of both Fe and Mn did not significantly affect the mechanical property of the
alloy when the ratio of Fe to Mn was constant. Microscopic analysis
showed that lowering the Fe level had effectively altered the morphology of the
β-AlFeSi needle
like structure. The β-AlFeSi
was found to be smaller in terms of size when Fe is lower, subsequently
reducing the probability of β-AlFeSi
phase to be stress riser and crack initiation. </p>
<p>The influence of heat treatment to the mechanical property of the alloys
was also studied. The mechanical result on the heat-treated samples indicated
that heat treatment is a viable method to improve the elongation property of
the alloy. Microscopic observations showed that the β-AlFeSi phase was broken into shorter structures
over the solution heat treatment process, resulting in better elongation. </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/9108284 |
| Date | 15 August 2019 |
| Creators | Mohamadrusydi B Mohamadyasin (7041476) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/DEVELOPMENT_OF_HIGH_DUCTILITY_ALUMINUM_ALLOYS_FOR_DIE_CASTING/9108284 |
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