Metallurgical Assessment of Novel Mg-Sn-La Alloys Produced by High-Pressure Die Casting

Abstract

Mg alloys containing Al are widely used for industrial applications, but the use of these alloys as an automotive part is limited due to the low melting temperature of the Mg17Al12 intermetallic phase. Therefore, magnesium alloys without aluminum that can withstand higher operating temperatures are of interest to the automotive industry. The objective of this work is to develop Al-free Mg alloys for industrial applications. In the current work, four types of alloys were produced with varying La contents. The high-pressure die casting method was selected to overcome the problems inherent in the gravity casting method with respect to the production of parts with complex shapes and thin walls. X-ray diffraction analysis revealed that the base alloy (Mg-5Sn wt%) comprises of alpha-Mg and Mg2Sn phases whereas La containing alloys included intermetallic phases such as LaMg3, Mg17La2, and La5Sn3. Corresponding grain sizes of the alloys with La are lower than those of the Mg5Sn alloy. Due to this lower grain size and emerging dispersoids, the tensile strength of the Mg5Sn4La alloy (205 MPa) is roughly double that of Mg5Sn. Moreover, the addition of the 4% wt. La to the Mg5Sn alloys led to an increase in yield strength and ductility by 25% and 50%, respectively.