中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
Vol. 21 No. 5 May 2011 |
crystal superalloy DD6
(National Key Laboratory of Science and Technology on Advanced High Temperature Structural Materials,
Beijing Institute of Aeronautical Materials, Beijing 100095, China)
Abstract:The second generation single crystal superalloy DD6 with 0.10%Hf and 0.34%Hf (in mass fraction) was subjected to high-cycle fatigue (HCF) loading at temperatures of 700 °C in ambient atmosphere. SEM was used to determine the initiation site and the failure mechanism. Evolution of the microstructure was investigated by TEM observation. The results show that fatigue limit of DD6 alloy with 0.34%Hf is a little smaller than that of the alloy with 0.10%Hf. The fatigue cracks initiated on the surface or near the surface of the specimens. The crack would propagate along {111} octahedral slip planes, rather than perpendicular to the loading axis of specimen. Typical fatigue striation formed in steady propagation of fatigue crack. The fracture mechanisms of the high cycle fatigue of DD6 alloys with 0.10%Hf and 0.34%Hf are quasi-cleavage fracture. Different types of dislocation structures were developed during high cycle fatigue deformation.
Key words: Hf; single crystal superalloy; DD6; high cycle fatigue