Low Cyclic Deformation Behaviour of Single Crystal Nickel Base Superalloys with Different Orientations at 980 ℃

Low cycle fatigue tests were conducted on different oriented single crystals of nickel base superalloy DD6 at 980 ℃ to study their cyclic deformation. Results show that at 980 ℃, the alloy with orientation of ［001］ exhibited cyclic hardening under higher total strain amplitude and cyclic stability under lower total strain amplitude, the same trend occurred in the specimens with ［011］ and ［111］ orientations. Strain rate could affect the cyclic hardening curve of the alloy. Under condition of low strain rate, the hardening curve moved upwards and the cyclic stress amplitude decreased. The higher the applied total strain amplitude, the more obviously the cyclic stress amplitude decreased. The higher strain rate made the initial hardening rate of the hardening curves increase under the same total strain amplitudes for both ［001］ and ［111］ oriented specimens, especially for the ［111］ oriented one.