The anomalous contraction on disordering Ni3Si

Zhou and Bakker (Acta Metall Maier 1994; 42:3009) reported the formation of progressively disordered L1(2) and also a distinct disordered fee solid solution on ball-milling Ni3Si with the ordered L1(2) structure. The formation of disordered phases was accompanied by a decrease in lattice parameter, 0.53% for partially disordered L1(2) at a 1ro parameter of similar to0.56, and as much as 2.44% for the disordered fee. These contractions were attributed to antisite defects. This behaviour is at variance with the generally observed small expansion on such disordering. Further, of the several L1(2) structures disordered by mechanical means, this is the only observation of the co-existence of a disordered L1(2) and a distinct disordered fcc phase. These results have been re-interpreted to show that the diffraction peak identified by them as characteristic of fcc in fact belongs to hexagonal Ni31Si12 phase, thus accounting for the major anomaly. The small decrease on partially disordering L1(2) is possibly due to an increase in the valence of Si. (C) 2003 Elsevier Science Ltd. All rights reserved.