Heat Capacity of Mg-Li Alloys with 21–30 at. pct Li in the Solid State

In the present study, the isobaric heat capacity of ultralight magnesium-lithium alloys with composition of 21, 25 and 30 at. pct Li were measured in the temperature range 185–775 K, most measurements were made for the first time. Measurements were performed by the method of differential scanning calorimetry using a DSC 404 F1 setup. The estimated uncertainty of the obtained results was 2–3 pct. The temperature dependences and the tables of recommended data on their basis were developed for scientific and practical application. For all studied Mg-Li alloys an abrupt change in the heat capacity was observed at the temperatures of about 220–260 K, which is apparently caused by the martensitic phase transformation. It was found that the specific molar heat capacity values of Mg-Li alloys containing 21–30 at. pct Li in the temperature interval of 250–685 K practically coincide with each other and can be estimated within the limits of DSC measurement uncertainties using the heat capacity temperature dependence of solid magnesium. It is possible to estimate the heat capacity of the studied alloys (with an accuracy not exceeding the measurement uncertainty) using the Neumann-Kopp rule, but in a much narrower temperature range of 250–456 K.