Heat capacity and phase equilibria in rare earth alloy systems. R-rich R-Al alloys (R=La, Pr and Nd)

Molar heat capacities of the R-Al (R=La, Pr and Nd) R-rich alloys were dete rmined at different temperatures by differential scanning calorimetry both by using the stepwise and the enthalpimetric methods. The results obtained for the molar heat capacity of alpha Pr3Al, beta Pr3Al and Nd3Al phases hav e been reported together with the values obtained for liquid La-Al alloys ( x(Al)=0.25). The characteristic temperatures obtained for the different inv ariant reaction involved in the R-rich region have been compared with the l iterature data. The alpha <----> beta Pr3Al transformation has been confirm ed at 330 degreesC and a value of Delta H-tr congruent to +0.09 kJ/mol of a toms obtained for the transformation enthalpy. (C) 2001 Elsevier Science B. V. All rights reserved.