Microstructure and properties of Mg-xSn-2La（x=2.34～9.36）alloy were investigated by OM（optical microscope）

SEM（scanning electron microscope）

XRD（X-ray diffraction）and EDS（energy dispersive spectrum）.It is found that with 2.34% Sn content

the alloy is mainly composed of α-Mg phase and Mg-La-Sn phase.With increasing in Sn content

Mg2Sn phase in the alloy is increased greatly and Mg-La-Sn phase is gradually coarsened

meanwhile

fine granular phase is decreased as rod-like phase increases.Furthermore

more RE phase tends to distribute along the interdentritic boundaries not to along grain boundary.In addition

tensile strength and elongation of the alloy are improved greatly with Sn addition.Mg-7.02Sn-2La alloy exhibits the optimum tensile strength of 151MPa while the Mg-4.68Sn-2La alloy shows the desirable elongation of 12.7%.However

excessive Sn addition can be detrimental to the mechanical properties of the magnesium alloy.