Simultaneously improving mechanical properties and electrical conductivity of Al-1.9Mn alloys with different Mg and Si addition

Abstract

A simultaneous achievement of high strength and toughness, as well as high conductivity in traditional Al-1.9Mn cast aluminum alloy used in the manufacture of water-cooled radiator shells has proven to be challenging. The addition of Mg and Si elements was implemented in the cast aluminum alloy for a modified treatment to solve the problem. The results showed that the inclusion of Si facilitated the transformation of the plate-like Mn-rich phase (Al6Mn) in the initial Al-1.9Mn alloy into a Chinese-script phase (Al15Mn3Si2) in the new Al-1.9Mn alloy. A higher Si content resulted in an increased volume fraction of Al15Mn3Si2 and a decreased solid solution of Mn in the matrix. Furthermore, a high content of Mg (0.9 wt%) in the Si modified Al-1.9Mn alloy resulted in a notable property reduction, not only in its elongation, but also in its electrical conductivity. It can be attributed to the formation of Mg2Si and the increased solid solution of Mg in the matrix. Through the optimization of the Mg and Si contents, new Al-1.9Mn alloys with superior mechanical properties and excellent electrical conductivity were successfully developed. With the addition of 0.45 wt% magnesium and 0.75 wt% silicon, the new Al-1.9Mn alloy increased its tensile strength to 170 MPa and yield strength to 88 MPa while maintaining 10 % elongation. At the same time, its electrical conductivity increased by 10.7 % compared to the original Al-1.9Mn alloy. The addition of magnesium and silicon elements can achieve a simultaneous enhancement of both the strength and electrical conductivity of the Al-1.9Mn alloy. This holds the potential to meet the usage requirements for cast aluminum alloys used in water-cooled radiator shells.