Alusil

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Alusil as a hypereutectic aluminium-silicon alloy (EN AC-AlSi17Cu4Mg / EN AC-48100 or A390) contains approximately 78% aluminium and 17% silicon. [1] [2] This alloy was theoretically conceived in 1927 by Schweizer & Fehrenbach, [3] of Badener Metall-Waren-Fabrik, [4] but practically created only by Lancia [5] in the same year, for its car engines. It was further developed by Reynolds, [6] now Rheinmetall Automotive. [2] In the United States, Chevrolet was the first to use Reynolds A390 in the Chevrolet Vega.

Contents

The Alusil aluminium alloy is commonly used to make linerless aluminium alloy engine blocks. [7] There is no coating applied to the cylinder bore and blocks are not honed conventionally. During the manufacturing process, a chemical or mechanical process is used to remove aluminum from the surface of the cylinder bore, exposing a very hard silicon precipitate. These exposed silicon particles, which under a microscope look like small islands, allow for oil to collect in the area surrounding them, thus forming the required tribofilm that supports piston and ring travel. [8]

The pistons used in an Alusil engine block typically have an iron-clad plating or similar coating on the piston skirts to prevent galling of the aluminum pistons when run against the uncoated aluminum cylinder bore. Examples of this coating include Mahle Ferrostan (I & II), FerroTec, or Ferroprint. [9]

BMW switched from Nikasil-coated cylinder walls to Alusil in 1996 to eliminate the corrosion problems caused through the use of petrol/gasoline containing sulfur.

Although similar, Alusil is not to be mistaken with Lokasil which was used by Porsche in the Boxster, Cayman, and 911 models from 1997 through 2008. Lokasil blocks use a freeze cast cylinder sleeve pre-form which is inserted into the casting mold. This preform contains silicon particles suspended in a resin binder. During the casting process, the molten aluminum is injected into the mold and burns off the resin, leaving an area of localized hypereutectic aluminum only in the area of the cylinder bore. The silicon particles are then mechanically exposed in a similar process to an Alusil block resulting in a cylinder block that functions in the same way as one cast out of Alusil.

Although successfully used by many European manufacturers, there are potentially issues associated with engines that use Alusil blocks, namely cylinder bore scoring which occurs when there is a breakdown of the exposed silicon particles in the cylinder bore, resulting in increased oil consumption and excessive piston noise. [10]

Vehicles / Engines using Alusil include:

See also

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References

  1. 1 2 3 "ALUSIL - Cylinder Blocks for the new Audi V6 and V8 SI engines" (PDF). KS Aluminium-Technologie AG. KSPG-AG.com. Retrieved 13 January 2010.[ permanent dead link ]
  2. 1 2 "What is Alusil coating?". finishing dot com. finishing.com. Retrieved 13 January 2010.
  3. 1 2 3 "Rheinmetall's tradition of automotive excellence". Rheinmetall Defence. Rheinmetall-Detec.de. January 2006. Archived from the original on 25 September 2006. Retrieved 23 May 2020.
  4. ↑ Addreßbuch Baden-Baden 1926 (PDF). Baden-Baden: Ernst Koelblin. pp. 49, 80, 185, 375.
  5. ↑ Manicardi N. (2014). Pionieri dell'automobile. Lancia, Bazzi, Ferrari. Modena (IT): Il Fiorino. ISBN   978-88-7549-464-3.
  6. ↑ "REYNOLDS 390 and A390". Alloy Digest. 20 (8). 1971-08-01. doi:10.31399/asm.ad.al0203. ISSN   0002-614X.
  7. ↑ "High-performance engine blocks for tomorrow's challenges". Kolbenschmidt Pierburg AG. KSPG-AG.com. 12 September 2005. Archived from the original on 2012-02-27. Retrieved 13 January 2010.
  8. ↑ "Latest machining techniques for aluminium cylinder bores (Alusil and Lokasil)" (PDF).
  9. ↑ Pistons and engine testing. MAHLE GmbH. Wiesbaden: Vieweg+Teubner. 2012. ISBN   978-3-8348-8662-0. OCLC   831115179.{{cite book}}: CS1 maint: others (link)
  10. ↑ Navarro, Charles (2019). "Understanding Bore Scoring in Al-Si Cylinder Systems" (PDF).
  11. 1 2 "KS Aluminium-Technologie: engine blocks for the new Audi A6". Rheinmetall AG. Rheinmetall.de. August 2004. Retrieved 13 January 2010.[ permanent dead link ]
  12. ↑ "High-tech products for the new and advanced BMW V12". Kolbenschmidt Pierburg AG. KSPG-AG.com. 10 January 2003. Archived from the original on 2012-02-27. Retrieved 13 January 2010.
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