Significant thinning of deformation twins and its effect on thermomechanical fatigue fracture in nickel base single crystal superalloys

The thermomechanical fatigue performances of two superalloys, TMS-82+ and TMS-196, were comparatively studied. The stress relaxation during the hold period and the plastic deformation in TMS-196 were both less than those in TMS-82+. The microstructural evolution was observed using scanning electron microscope and transmission electron microscope. It was found that numerous thin twins were formed during the tests in TMS-196, while in TMS-82+, few thick twins were developed. Moreover, the fracture surface of TMS-82+ is relatively flat, whereas the fracture surface of TMS-196 is rather rough. This difference was attributed to their different twin morphologies. Given their different compositions and properties, this research may provide useful guidance for the further development of superalloy.