First principles phase stability calculations are used to predict the lattice mismatches between Nb and the A2 (Hf1-x Zrx) Al L 21 Heusler phases and the L 21 phase formation energies, where A=Pd andor Pt, and x=0, 0.25, 0.75 and 1. The calculated L 21 phase mixing energy demonstrates that the Hf-Zr solution phases in the form of A2 (Hf1-x Zrx) Al (x≠0 and 1) are energetically favored, although the Zr-rich alloys exhibit a smaller lattice mismatch than the Hf-rich alloys. The introduction of Pt reduces the lattice mismatch, and forms the energetically favorable (PtPd)XAl Heusler phase, where X=Hf and Zr. A number of critical diffusion couple experiments confirm the phase stability predictions and establish new microstructural design parameters.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)