Every Engineer is vitally concerned with the materials and their properties. Whether he has to manufacture a bridge, a machine or an automobile part, he must have an intimate knowledge to select suitable material for his products according to the requirements. In selecting a particular material, properties such as machinability, mechanical stability, chemical durability, electrical resistivity and thermal conductivity as well as cost of the material should be considered.

Aluminum alloys and other lightweight aluminum alloy materials have growing applications in the automotive industry, with respect to reducing the fuel utilization and shielding the environment, where they can successfully reinstate steel and cast iron parts. These alloys are extensively used in buildings and constructions, containers and packaging, marine, aviation, aerospace and electrical industries because of their lightweight, corrosion resistance in most environments, or combination of these properties. Aluminum based alloy provides good combination of strength, corrosion resistance, along with fluidity and freedom from hot shortness.

Aluminum alloys are distinguished according to their major alloying elements. Silicon is good in metallic alloys. This is because it increases the fluidity of the melt, reduces the melting temperature, decreases the shrinkage during solidification and is very inexpensive as a raw material. Silicon also has a low density, which may be an advantage in reducing the total weight of the cast component. Silicon has a very low solubility in aluminum; it therefore precipitates as virtually pure silicon, which is hard and hence improves the abrasion resistance.

Mechanical properties are controlled by the cast structure. Microstructure evolution of hypoeutectic Al–Si alloys during solidification is in two stages: primary dendrite Al–phase formation (α–matrix), and the subsequent eutectic transformation (eutectic Si particles in α–matrix). The mechanical properties of Al–Si alloys depend, more on the distribution and the shape of the silicon particles.

The mechanical properties of the Al- Si alloy are dependent on the size, shape and distribution of eutectic and primary silicon particles. Small, Spherical, uniformly distributed silicon particles enhance the strength properties of Al-Si alloys.

From article:" Impact of Silicon Content on Mechanical Properties of Aluminum Alloys".