Effect of Solidification Rate on Microstructure and Mechanical Characteristic of Gray Cast Iron

In this study, various solidification rates were achieved by controlling the wall thickness to improve the hardness properties of gray cast iron (GCI). The effects of solidification rate on the microstructure and mechanical properties of GCI were investigated through Optical microscope, Scanning electron microscope, Thermal analysis, etc. Experimental results showed that the hardness improved as the solidification rate increased. Higher solidification rates were found to refine austenite, graphite, pearlite and eutectic cell size, reduce pearlite lamellar spacing, and increase pearlite and eutectic cell count. The increasing solidification rate resulted in the carbon released by the austenite accumulation along the austenite dendrites, which caused type D graphite formation. In addition, it was also found that the primary dendrite arm spacing (DAS), secondary dendrite arm spacing (SDAS) and eutectic cell size decreased as the hardness increased. Thermal analysis revealed that the increased solidification rate reduced the austenite precipitation, eutectic nucleation and eutectic minimum temperature, resulting in an improvement of the undercooling, thus accelerating the solidification and crystallization process.