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DRSA Inreach

Internal Stresses in Aluminum Engines. Solidification. DRSA Inreach. Outline. Introduction to solidification of casting alloys. Phase diagram for Al-Si. Phases during cooling. Different cooling rates throughout cast engine head. Phases. Melting and Boiling Temperatures. Phases.

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DRSA Inreach

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  1. Internal Stresses in Aluminum Engines Solidification DRSA Inreach

  2. Outline • Introduction to solidification of casting alloys. • Phase diagram for Al-Si. • Phases during cooling. • Different cooling rates throughout cast engine head.

  3. Phases

  4. Melting and Boiling Temperatures

  5. Phases • Simple systems have a melting temperature and a boiling temperature • Engines made from alloy of aluminum and silicon • More complicated in alloys

  6. Alloys • What is an alloy • Not a compound • H2O • CH4 • Mixture of two or more metals in any proportion • Aluminum too soft, weak • Add silicon to harden and strengthen

  7. Alloys • Aluminum and silicon come out of the melt and form separate components at the microscopic level • Rather than melting and boiling temperatures, look at Phase Diagrams

  8. Al-Si Phase Diagram

  9. Al-Si Phase Diagram Eutectic Liquidus Solidus

  10. Microstructure Al-19%Si

  11. Engine Head

  12. Internal Stresses • Outside cools first • Solid outer shell • Molten inner core, cools later, puts outer shell in tension • Different cooling rates lead to different microscopic structures • Mismatch in microscopic structures create internal stresses

  13. Next Week… • …Stresses and Strains

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