Study on the effect of cooling rate on the solidification parameters, microstructure, and mechanical properties of LM13 alloy using cooling curve thermal analysis technique

• Investigation of all of solidification parameters at different cooling rates.
• Finding characteristic equation between SDAS and cooling rate.
• Introducing new factor for distribution of primary silicon.
• Finding relation between cooling curve and eutectic morphology and porosities.
• Studying the effect of cooling rate on mechanical properties using shear punch test and microhardness.

In this study, the effect of cooling rate on the microstructure, solidification parameters, and mechanical property of LM13 alloy has been investigated. To obtain different cooling rates, an air-cooled graphite mold, 3 sand molds with different moisture content, a water-cooled graphite mold, and a water-cooled steel mold were used. The cooling rates and the solidification parameters were determined by using computer-aided thermal analysis method. Results show that with increasing cooling rate from 1.1 to 50 °C/s, secondary dendrite arm spacing decreases 65%. At higher cooling rates, the nucleation temperature of reactions shifts to higher temperature, except the final reaction, but the eutectic recalescence undercooling is eliminated. It modifies eutectic microstructure and decreases parallel eutectic layers distance from 23.24 to 4 μm. In addition, it reduced primary silicon particle appearance (PSPA) from 1.17 to 0.3. The equivalent porosity diameter also reduces from 72.5 μm to 27.8 μm. Shear punch test (SPT) shows improvement of ultimate shear stress, yield shear stress, and normalized displacement at higher cooling rates. Hardness has also been improved about 30 Vickers as a result of increasing cooling rate.