Relationship between tensile and primary creep properties of near γ-TiAl intermetallics

This paper presents the tensile and primary creep behaviour of fully lamellar microstructures for three near, gamma -TiAl compositions: binary TiAl, ternary TiAl + W and TiAl + NbMnWMoSi. Reducing the lamellar interface spacing or aging to precipitate beta along interfaces increases the 760 C tensile strength. Primary creep at stresses from 140 to 276 NlPa and 760 degreesC is characterized in terms of the instantaneous strain occurring during creep loading and a subsequent primary transient. The presence of interface beta precipitates reduces the instantaneous strain and increases the time to 0.5% creep strain. Reducing lamellar interface spacing does not influence the instantaneous strain, but decreases the strain rate during the primary transient. Correlating the creep response with deformation structures after primary creep suggests that the instantaneous strain depends on the mobility of interface dislocations and the primary transient depends on dislocation mobility in both the lamellar interfaces and gamma lamellae. (C) 2001 Elsevier Science Ltd. All rights reserved.