Enhanced mechanical properties and thermal conductivity of high-pressure die-cast AlMg6Si2MnZr alloy by controlling the externally solidified crystals

Abstract

In this work, better mechanical properties and thermal conductivity of the high-pressure die-cast AlMg6Si2MnZr alloy were reported by replacing the conventional H13 steel shot sleeve with a new ceramic type shot sleeve (named LX shot sleeve). The work mainly concentrated on the effect of microstructure on the mechanical properties and thermal conductivity of two die-cast samples of AlMg6Si2MnZr alloy by different shot sleeves. The results showed that the LX shot sleeve produced smaller and fewer externally solidified crystals of α-Al (ESCs-α) as it dissipated heat more slowly than the H13 shot sleeve. Meanwhile, ESCs-α in the die-cast sample by the LX shot sleeve had lower dendritic branching extent. Due to the decrease in ESCs-α, the eutectic content and the number of the porosities, particularly shrinkage porosities, of the die-cast sample by the LX shot sleeve decreased. The mechanical properties of the die-cast sample by the LX shot sleeve were increased greatly, particularly the elongation, which was increased from 6.64% to 9.06% due to the decrease in the shrinkage porosities. The thermal conductivity of the die-cast sample by the LX shot sleeve was also increased from 112.2 W m −1 K −1 to 120.6 W m −1 K −1 . In the die-cast sample by the LX shot sleeve, the decrease in the Mg solute concentration in α-Al solidified in the cavity (α) was the main factor to distinctly increase the electrical thermal conductivity while the reduction of the eutectic phase resulted in a slight decrease in the phonon thermal conductivity. • The difference in the microstructure of samples of HPDC AlMg6Si2MnZr alloy by different shot sleeves is studied. • Mechanical properties and thermal conductivity are improved using a new LX shot sleeve. • Large-size shrinkage porosity in the center is the crack source and reduces the elongation. • Electrical thermal conductivity increases sharply and phonon thermal conductivity decreases slightly using the LX sleeve. • Higher Mg solute concentration in the sample using the H13 shot sleeve is the main factor to reduce thermal conductivity.