Silicon-Rich Structural Alloys

Technology #13605

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Inventors
Professor Christopher Schuh
Department of Materials Science and Engineering, MIT
External Link (dmse.mit.edu)
David Fischer
Department of Materials Science and Engineering, MIT
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Silicon-Rich Alloys

US Patent Pending 2012-0238439
Publications
Microstructure and Fracture of Anomalous Eutectic Silicon-Disilicide Composites
Intermetallics, November 2011, p. 1661
Effect of a Rising R-Curve on the Sliding Wear of Silicon-Disilicide In Situ Composites
Journal of American Ceramic Society, April 2012, p. 1406

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