Phase Equilibria and Melting of Aluminum-Rich Al-Nd-Ti Alloys

The aluminum-rich portion of the Al-Nd-Ti system was investigated experimentally with a focus on solid-liquid phase equilibria. Thermal analysis, electron-microscopy and X-Ray diffraction experimental techniques were employed for that purpose. The experimental results were interpreted with the aid of thermodynamic modeling and ab initio (DFT) calculations. In addition to the phases appearing already in the included binary systems, two ternary phases, Al20Ti2Nd and Al43Ti4Nd6, were observed. We confirm that both these phases are stable and should be included in the equilibrium phase diagram. However, the formation of the Al43Ti4Nd6 phase is sluggish and requires a thermal treatment. Both the Al20Ti2Nd and Al43Ti4Nd6 phases melt by peritectic reactions at T = 970 +/- 10 degrees C and 1013 +/- 5 degrees C respectively. The Gibbs energy of the ternary phases was determined by the fitting of the parameters of a thermodynamic model to experimental results, and through the results of ab initio calculations. The Al-rich portion of the phase diagram was calculated with the use of the calibrated model.