Effect of Cooling Rate on the Microstructure and Solidification Characteristics of Al-20%Mg2Si In Situ Composites Using Computer-Aided Thermal Analysis Technique

The formation, size and morphology of Mg2Si intermetallics as the reinforcement particles in Al-Mg2Si in situ composites have important effects on the mechanical properties of the alloy. Solidification conditions, particularly cooling rate, have a direct effect on the microstructure and characteristics of the reinforcement particles. In this research, the effect of different cooling rates on the microstructure and solidification parameters of Al-20%Mg2Si in situ composite has been investigated using cooling curve thermal analysis technique. For this purpose, the thermal analysis curves of this composite have been plotted at five different cooling rates. The results demonstrated that the variation of cooling rate affects the characteristic temperatures of primary Mg2Si phase and the eutectic reactions. By increasing the cooling rate from 0.4 to 17.1 degrees C/s, the nucleation temperature of primary Mg2Si, binary eutectic and ternary eutectic is increased, while growth temperature of both eutectic reactions is decreased. Also, Mg2Si reinforcement particles changed from coarse dendritic to fine polygonal shape accompanied with decrease in size and increase in density.

Automated summary

The formation, size, and morphology of Mg2Si intermetallics in Al-Mg2Si in situ composites significantly influence the mechanical properties of the alloy. Cooling rate during solidification has a direct impact on the microstructure and characteristics of the reinforcement particles. This study investigated the effect of different cooling rates on the microstructure and solidification parameters of Al-20%Mg2Si in situ composite using cooling curve thermal analysis technique. The results showed that increasing the cooling rate resulted in higher nucleation temperature of primary Mg2Si, binary eutectic, and ternary eutectic, while decreasing the growth temperature of the eutectic reactions. Furthermore, the Mg2Si reinforcement particles changed from coarse dendritic to fine polygonal shape, accompanied by decreased size and increased density.