Density and Thermal Expansion of Mg–Li Alloys with Lithium Content Up to 30 at%

Abstract

An experimental study of the relative elongation and the thermal expansion of a number of the magnesium–lithium alloys containing 5, 10, 17, 21, 25, and 30 at% lithium in a wide temperature range from 100 K to 650 K was carried out using the dilatometric method. The density of the alloys at room temperature was measured using the Archimedes method. The temperature and composition dependences of the studied properties were constructed using the obtained results. A comparison with literature results and an analysis of the behavior of the density and the linear thermal expansion coefficient (LTEC) of the Mg–Li alloys with an increase in lithium content to 30 at% (11 wt%) were carried out. It was shown that the addition of lithium up to 17 at% has virtually no effect on the LTEC value. Whereas in the range of 17 at% to 30 at% Li, the change in the LTEC value of the alloys reaches up to about 40%. It was found that in the Mg–Li alloys with a lithium content of 21 at% to 30 at% a phase transition occurs in the range of 226 K to 248 K, where the linear thermal expansion coefficient change abruptly. Moreover, the magnitude of the LTEC jump increases with lithium content. This kind of transition was found earlier in the study of the Mg–Li eutectic alloy and is presumably related to the martensitic-type transformation of the lithium-rich bcc magnesium–lithium alloys to the hcp structure.