Silicon-rich Structural Alloys

Applications

This technology is applicable to medium stress structural materials to make components, such as break pad and engine blocks, lighter and cheaper.

Problem Addressed

Silicon, the second most abundant element on earth, exhibits the strength, high hardness, and low density of popular engineering ceramics but is much cheaper to manufacture and process, thus making it a promising material for many mechanical and structural applications.  However, pure silicon is fairly brittle at room temperature, which limits its usefulness as a structural material.  This technology develops silicon-based alloys containing at least 50% silicon by weight, which allows the alloy to benefit from silicon's low density and price while not suffering from the brittleness of pure silicon.

Technology

Pure silicon can withstand large stresses before permanently deforming.  However, this high strength makes silicon very brittle since a small amount of deformation would dissipate local concentrations of high stress and, as a result, slow down crack propagation.  This technology alloys silicon with other elements to reduce brittleness.  When silicon is melted with another element at the eutectic composition and cast into a mold, cubic silicon and silicide phases can exist simultaneous in the cooled structure.  The silicide phases serve as obstacles to crack propagation and helps to bridge cracks by slightly delaminating when the structure is under high stress.  These mechanisms hinder the spread of microscopic cracks and allow the alloy to be several times tougher than pure silicon.

Advantages

  • High-toughness silicon-based alloys
  • Light-weight and cheap structural material
  • Can be manufactured through low-cost casting processes