High temperature deformation behaviors of a high Nb containing TiAl alloy

Abstract

In the present paper, high temperature tensile and creep behaviors of Ti–45Al–9(Nb,W,B,Y) alloy with duplex (DP) microstructure were investigated. In addition to tensile tests at 815 °C and a strain rate range of 1 × 10 −4 s −1−1 × 10 −3 s −1 and tensile, creep tests at 760 °C and 815 °C under the stress of 180 MPa, the microstructure evolutions during tensile and creep tests were studied. The results show that high temperature high Nb containing TiAl alloy with DP microstructure has a good balance between ductility and strength and intermediate creep resistance. The tensile properties have the strain rate dependence, and ultimate tensile strength (UTS) and yield strength (YS) vs. strain rate obey a single-logarithm linear relationship. Minimum creep rate is affected by the test temperature and stress. Using loading change experiment a stress exponent of 4.3 is determined. DP microstructure is unstable after long-term exposure at high temperatures, and the spheroidization of lamella and recrystallization along grain boundaries occur during the high temperature deformation. It is assumed that the diffusion-assisted climb of dislocations might be the controlling mechanism at the minimum creep rate stage.