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How is silicon used as an alloying element in steel, aluminum, brass, and bronze?

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A periodic table element square for silicon shows atomic number 14, symbol Si, atomic weight range, electron configuration, and name. Icons indicate it is a solid nonmetal with diamond crystal structure and equal relative strength. Labels explain each property. — silicon Chemical properties of the element silicon.

Silicon serves as a vital alloying element across various metals, primarily valued for its ability to improve casting qualities, strength, and corrosion resistance.

Steel

In steelmaking, silicon is often added as a ferroalloy, such as ferrosilicon, to act as a deoxidizer, removing oxygen from the molten metal. It is also used in combination with manganese as silicomanganese, which is highly effective at producing low-melting silicates that separate easily from the steel.12

Aluminum

Silicon is a major alloying element in aluminum, particularly for foundry alloys. It imparts great fluidity to molten aluminum, making it ideal for welding wire, brazing materials, and intricate castings. In 6XXX series wrought alloys, silicon is combined with magnesium to form $M g_{2} S i$ particles, which allow the metal to be strengthened through thermal treatment.3

Brass and Bronze

Silicon Bronze: These alloys typically contain about 96 percent copper and are prized for their exceptional corrosion resistance, strength, and ease of welding.4
Brass and Copper: Silicon copper alloys (containing 20 to 30 percent silicon) are used as ingredients to remove oxygen from molten copper or brass.5