Microstructures and Properties of High Performance Cast Irons Applied in Automobile Flywheels
High performance cast iron (HPCI) with improved mechanical properties and balanced thermal conductivity is a strong candidate to replace ductile iron in the application of automobile flywheel. In this work, the relationship between microstructures and properties, including mechanical and thermal properties, of the grey cast iron were investigated by analysing some commercial flywheels. The results showed that the content of graphite was dependent on the content of carbon in the grey cast irons, and the simulation results indicated that most of carbon directly formed into graphite at room temperature (RT). High ultimate tensile strength (UTS) is caused by low area fraction and short length of the graphite. The thermal conductivity increased with increase of the area fraction of graphite. The short length of graphite would also contribute to thermal conductivity since a large number of the short graphite flakes formed under the circumstance of the similar area fraction of graphite. In order to get HPCI, the microstructures with a moderate area fraction and short length of graphite should be controlled.
KeywordsHigh performance cast iron (HPCI) Grey cast iron Microstructure Type A graphite Thermal conductivity Ultimate tensile strength
The authors would like to acknowledge W. Y. Yang and Y. R. Zheng for the assistance of useful discussions. The financial support provided by Ford Motor Company (University Research Program, 2014-5121R) is also acknowledged.