Mg-20 Cu-8 Sn and Mg-15 Ca-5 Sn alloys for magnesium based thermal storage materials were designed.Densities of two alloys were measured by drainage method.The microstructure

phase composition of the two alloys are characterized by metallographic microscope（OM）

X-ray diffraction（XRD）and electron microprobe（EPMA）.And thermal phase change temperature

latent heat were measured by differential scanning calorimetry（DSC）.The results show that the densities of Mg-20 Cu-8 Sn and Mg-15 Ca-5 Sn alloys reach 2.133 g/cm3 and 1.695 g/cm3

respectively.Mg-20 Cu-8 Sn alloy is composed ofα-Mg+CuMg

2

+Mg

2

Sn and Mg-15 Ca-5 Sn consists ofα-Mg+MgCa2+Mg

2

Sn.The phase transition temperature and latent heat of the two alloy are 462.42

517.37 ℃ and 136.4

195.1 J/g

respectively.