Generalized planar fault energies and mechanical twinning in gamma TiAl alloys

We calculated generalized planar fault energies along 1/6 < 11-2](111) true- and 1/6 < 1-21](111) pseudo-twinning directions and correlated with the propensity for mechanical twinning in gamma TiAl alloys with different Al contents. The generalized planar fault energies along 1/6 < 11-2](111) increase with increasing Al content. The predicted critical twinning stresses show that hypostoichiometric TiAl undergoes twinning more readily than stoichiometric and hyperstoichiometric TiAl. The critical stresses for 1/6 < 1-21](111) are dramatically larger than those for 1/6 < 11-2](111), and thus twinning occurs through energetically favorable 1/6 < 11-2](111). (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.