Effect of electron concentration on the phase stability of NbCr2-based Laves phase alloys

The phase stability in NbCr2-based transition-metal Laves phases was investigated, using data from binary X–Cr, Nb–X, and ternary Nb–Cr–X phase diagrams. It was shown that when the atomic size ratios are kept identical, the average electron concentration factor, e/a, is the dominating factor in controlling the phase stability of NbCr2-based transition-metal Laves phases. The e/a ratios for different Laves polytypes were determined as follows: with e/a<5.76, the C15 structure is stabilized; at an e/a range of 5.88–7.53, the C14 structure is stabilized; with e/a>7.65, the C15 structure is stabilized again. A further increase in the electron concentration factor (e/a>8) leads to the disordering of the alloy.