Modeling the formation of twins and stacking faults in the Ag-Cu system

In forming new grains, both in solid slate reactions and in solidification, the formation of twins or stacking-faults is of considerable interest. In the present work, a terrace/ledge nucleation model is used to explore the relationship between the degree of undercooling and the probability of forming twins or stacking-faults, and compared with experimental results for rapid solidification of several alloys in the two-phase Ag-Cu system. The model is consistent with the experimental results and indicates that at an undercooling between 37 K and 55 K, twins or stacking-faults form first in the Ag-rich solid solution. Larger undercooling brings about the formation of twins or stacking-faults in the Cu-rich solid solution. The degree of undercooling required for defect formation can be related to the stacking fault or twin boundary energies of the materials. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.