Mg-Li-Ca Eutectic Alloy. Phase Transitions and Thermophysical Properties

A homogeneous eutectic alloy of the magnesium-lithium-calcium ternary system containing 72.5 at.% magnesium, 19.1 at.% lithium, and 8.4 at.% calcium was prepared. Experimental studies of the relative elongation, density, thermal expansion, heat capacity, thermal diffusivity and thermal conductivity of this ultralight alloy were performed in the temperature range of 120 K to 710 K. The behavior of density and thermal expansion in the melting-crystallization region and in the liquid state was also studied. A comparison with previously obtained results on the thermophysical properties of pure magnesium and magnesium-lithium, magnesium-calcium eutectic alloys was made. The temperature dependences were constructed and the table of the investigated properties recommended values were presented. It was found that in the Mg-Li-Ca alloy a phase transition occurs in the range of 225 K to 245 K, where the heat capacity and the linear thermal expansion coefficient change abruptly. This kind of transition was found earlier in the study of the Mg-Li eutectic alloy and is presumably related to the martensitic transformation of the lithium-rich bcc magnesium-lithium alloys to the hcp structure.