Microstructural anisotropy, uniaxial and biaxial creep behavior of Ti–45Al–5Nb–0.2B–0.2C

In order to study the effect of microstructural anisotropy on the high temperature behavior of titanium aluminides, uniaxial tensile and biaxial (double shear) creep experiments were conducted on a hot-extruded Ti–45Al–5Nb–0.2B–0.2C (at.%) alloy in the temperature range between 700 and 800 °C. The material initially exhibits an anisotropic duplex microstructure which affects the creep behavior under uniaxial loading conditions. In contrast, no influence of specimen orientation was found in double shear creep testing. Only the uniaxial creep data from specimens extracted parallel to the extrusion direction can be unified with the shear creep data by using a simple von Mises criterion. The creep data sets from tensile specimens oriented perpendicular to the extrusion direction do not match these master curves. This shows that it is not straightforward to apply simple reference stress criteria in cases where materials are textured. We discuss these findings considering local stress states and microstructures.