A study of high-Co Al-Ni-Co decagonal phase

The stability and transformation behavior of the decagonal phase was studied at the composition Al72Co15.5Ni12.5. Similarly to the decagonal phase at high Ni-contents, it can transform with partitioning. The transformation requires significantly longer annealing times (up to several thousands of hours) and for the studied compositions results in the formation of the X-phase and the decagonal phase with higher-Ni composition than the initial decagonal phase. For shorter times, formation of a series of intermediate metastable states is observed. Some of them are identified with the structures reported earlier, to be specific variants of the high-Co decagonal phase. (C) 2002 Elsevier Science B.V. All rights reserved