Creep of a TiAl alloy: a comparison of indentation and tensile testing

Abstract

The present study compares the indentation and uniaxial creep behaviour of a near-γ-TiAl alloy with a duplex microstructure. Indentation creep tests were performed using a cylindrical indenter at temperatures between 750 and 1050 °C and net section stresses between 50 and 1430 MPa. A stress dependent stress exponent ranging from 3 for low net section stresses to 8 for high net section stresses was determined. The apparent activation energy of indentation creep was determined as 343±16 kJ mol −1. The stress as well as the temperature dependence of the indentation and uniaxial creep data are in good agreement. The indentation experiments were also analysed with respect to the deformed volume in front of the indenter and the surface bulge that develops around the indenter. A simple dislocation model is proposed to rationalize volume and shape of the bulge around the indenter. The good agreement of creep parameters obtained by indentation and conventional uniaxial creep testing demonstrates that indentation creep tests are suitable to characterize creep.