Role of grain boundaries in the high-temperature performance of a highly stabilized beta titanium alloy II: Creep behavior

Two different microstructures, with straight and bending grain boundaries, were obtained after two typical heat treatments: (1) annealing treatment (AnT) at 600 °C for 4 h followed by air cooling and (2) solution treatment (S-AT) at 850 °C for 1 h, followed by water quenching, an aging treatment at 550 °C for 6 h and air cooling. Creep performance was tested for samples of the alloys with different grain boundary morphologies, and the results show that the grain boundary morphology plays an important role in creep performance. The alloy with a bending grain boundary microstructure after AnT showed better creep resistance at lower temperature levels, while the alloy with a straight grain boundary microstructure after S-AT showed better creep resistance at higher temperature levels. These observations mainly result from the changes in creep cavity behavior, internal stresses and precipitation strength for curved and straight grain boundary microstructures with increasing creep temperature.