THE HEXAGONAL METASTABLE PHASE FORMED IN AN AMORPHOUS Ni-P ALLOY DURING CRYSTALLIZATION (Ⅲ)——HEXAGONAL POLYTYPE

Abstract

By tilting the crystals formed in an amorphous Ni-P alloy during crystallization in transmission electron microscope, two further hexagonal metastable phases (a2 and a3) have been discovered. Their lattice parameter a has the same value (6.73?) as that of the previously reported hexagonal metastable phase (a1), but the values of the other lattice parameter c are 3/2 and 4 times respectively of that of the phase a1. This shows that these phases are longperiod polytype structures. Furthermore, the previously assumed F.C.C. sublattice (a=5.50?) of a1 has been found to be really metastable phase from {111} planes of which these hexagonal metastable phases are formed.