Deformation of polysynthetically twinned (PST) TiAl crystals at high strain rate and high temperature

Deformation microstructures in a 45°〈3̄21〉 oriented (the lamellar interface was tilted 45° from the loading axis about the 〈3̄21〉 direction in the lamellar interface) polysynthetically twinned (PST) TiAl crystal deformed in compression at 3000 s^-1 and 800°C was studied. Deformation of this PST crystal is characterized as follows: 1) Deformation of domains [III] and [IV] is dominated by 1/6 [112̄](111) parallel twinning (twinning parallel to lamellar interfaces). Ordinary dislocations observed in these domains are found to be a complementary deformation mode. 2) Deformation of domains [II], [V] and [VI] is controlled by a 1/2 〈110] ordinary dislocation slip. Complementary deformation modes in these domains are ordinary dislocation slip, superdislocation slip and cross-twinning. 3) Domain [I] is not deformed after the specimen deforms up to approx.7% strain.