High thermal conductivity and high strength magnesium alloy for high pressure die casting ultrathin-walled components

With the rapid development of 3C industries, the demand for high-thermal-conductivity magnesium alloys with high mechanical performance is increasing quickly. However, the thermal conductivities of most common Mg foundry alloys (such as Mg-9wt%-1wt%Zn) are still relatively low. In this study, we developed a high-thermal-conductivity Mg-4Al-4Zn-4RE-1Ca (wt%, AZEX4441) alloy with good mechanical properties for ultrathin-walled cellphone components via high-pressure die casting (HPDC). The HPDC AZEX4441 alloy exhibited a fine homogeneous microstructure (average grain size of 2.8 mu m) with granular Al11RE3, fibrous Al2REZn2, and networked Ca6Mg2Zn3 phases distributed at the grain boundaries. The room-temperature thermal conductivity of the HPDC AZEX4441 alloy was 94.4 W center dot m(-1)center dot K-1, which was much higher than 53.7 W center dot m(-1)K(-1) of the HPDC AZ91D alloy. Al and Zn in the AZEX4441 alloy were largely consumed by the formation of Al11RE3, Al2REZn2, and Ca2Mg6Zn3 phases because of the addition of RE and Ca. Therefore, the lattice distortion induced by solute atoms of the AZEX4441 alloy (0.171%) was much lower than that of the AZ91D alloy (0.441%), which was responsible for the high thermal conductivity of the AZEX4441 alloy. The AZEX4441 alloy exhibited a high yield strength of similar to 185 MPa, an ultimate tensile strength of similar to 233 MPa, and an elongation of similar to 4.2%. This result indicated that the tensile properties were comparable with those of the AZ91D alloy. Therefore, this study contributed to the development of high-performance Mg alloys with a combination of high thermal conductivity, high strength, and good castability.

Automated summary

With the rapid development of the 3C industries, there is a growing demand for high thermal conductivity magnesium alloys with high mechanical performance. In this study, a high-pressure die casting AZEX4441 alloy with good mechanical properties and high thermal conductivity was developed for ultrathin-walled cellphone components. The alloy exhibited a fine microstructure and higher thermal conductivity compared to traditional alloys.