English abstract
Aluminum alloys are extensively finding applications in many industries, including
automotive and aerospace, because of its lightweight. However, still, Al alloys suffer from lower
strength, and finding a suitable alloy composition is quite critical. In this research, a novel
aluminum alloy was produced using a stir squeeze casting technique. Sustainability analysis of
three competing processes to produce the alloy was carried out using Analytical Hierarchy Process
(AHP) method. Based on the final scores obtained through AHP, the stir-squeeze casting was
selected to produce the Al- High Entropy Alloy (HEA). The optimal conditions for the stir-squeeze
casting process parameters were determined from the literature. Scrap aluminum alloy wheels
(typically A356 grade) from cars were used as the matrix material. High entropy alloy (HEA) was
used as the alloying element, with a total weight percentage of 2.6 %. The composition of the HEA
is Al35 Li20 Mg15 Si10 Zn15 Ca. After the alloy is developed, mechanical properties such as hardness,
tensile, wear, and compression tests were conducted. Besides, the microstructure of the developed
material was studied. Optical microscope and Scanning Electron Microscope (SEM) as well were
used for the analysis. Moreover, X-ray Diffraction (XRD) was carried out to analyze the phases
formed during alloy development. In addition, heat treatment was done for the produced alloy, and
then mechanical properties and microstructure were compared before and after heat treatment. T6
heat treatment was completed which includes two main steps, solution treatment followed by
quenching and then aging. The mechanical properties before heat treatment were sufficient enough
when compared to the original A356 (LM25) grade that is not heat treated. After heat treatment,
there was a significant improvement in hardness and compressive strength, and this improvement
is mainly attributed to the Si particle precipitation that occurred during the aging process. Both
before and after heat treatment, the fracture appeared to be brittle. The reason for the brittle fracture
is attributed to the accumulation of second phases in the grain boundaries, which have weak
bonding with the matrix material. The developed novel Al-HEA alloy can be deployed in several
applications where compressive strength is of primary importance, such as car alloy wheels,
cylinder heads and blocks.
