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Gu Y.-L.,Aerospace Research Institute of Materials And Processing Technology | Gu Y.-L.,Failure Analysis Center | He Y.-H.,Aerospace Research Institute of Materials And Processing Technology | He Y.-H.,Failure Analysis Center | And 5 more authors.
Advanced Materials Research | Year: 2013

Low cycle fatigue failure tests of the powder metallurgical nickel based superalloy FGH96 at 550°C and 720 °C were carried out under total strain-controlled mode (R=-1). The fatigue failure behaviors were investigated by analyzing cyclic stress response and observing microstructure after fatigue through scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results show that FGH96 superalloy exhibits cyclic stability at 550 °C, and cyclic softening afterwards at 720 °C with Δε/2=0.4%, and of cyclic softening at 720 °C with Δε/2=0.7%. After high temperature low cycle fatigue, the γ′ precipitates are cuboidal for all samples. No coarsening of γ′ precipitates was detected at 550 °C and at 720 °C with Δε/2=0.4%, but small γ′ precipitates get together to be larger precipitates at 720 °C with Δε/2=0.7%. EBSD shows that the continuous small angle grain boundaries are produced during the fatigue. The small angle grain boundaries have a significant increase at 720 °C, especially that case at Δε/2=0.7%.© (2013) Trans Tech Publications, Switzerland. Source


Gu Y.,Touch Stone Testing Innovation Corporation | Teng X.,PLA Representative Office at AVIC South Aviation Industry Ltd Corporation | Liu C.,Touch Stone Testing Innovation Corporation | He Y.,Touch Stone Testing Innovation Corporation | Tao C.,Touch Stone Testing Innovation Corporation
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2012

Directionallly solidified superalloy DZ125 is aged at 950°C for 500 h, 1000 h and 1500 h, respectively. The ultra-high cycle fatigue property of alloy DZ125 is measured using an ultrasonic fatigue test machine. The microstructures and ultra-high cycle fatigue behaviors of DZ125 are investigated using scan electron microscopy, transmission electron microscopy and electron backscatter diffraction (EBSD) technique. The results show that the effect of long-term aging heat treatments on the microstructures of DZ125 is small, and the lattice misfit is reduced after long-term aging. With the increase of the aging time, γ' phases accumulate and grow obviously, but the topologically close packed(TCP) phase is not found. The effect of long-term aging heat treatments on the ultra-high cycle fatigue properties is small. With the increase of the aging time, the ultra-high cycle fatigue property shows a downward trend .The fatigue fracture surface is perpendicular to the stress axis/fatigue cracks initiate from the sample surface, and the grain rotation angle is small after ultra-high cycle fatigue tests. Source


Liu X.,Aerospace Research Institute of Materials And Processing Technology | Liu X.,Touch Stone Testing Innovation Corporation | Tao C.,Aerospace Research Institute of Materials And Processing Technology | Tao C.,Touch Stone Testing Innovation Corporation
Advanced Materials Research | Year: 2011

Analyze and represent the main problem about aviation material application, that is the low readiness and large dispersity. Technology readiness assessment and the universal technology readiness level standard of USA are introduced. On the basis of analysis and studying the aviation material engineering application and according to 9-level technology readiness standard, we put forward material readiness level and level entries, using which you can assess material readiness straightway. We also put forward material readiness assessment method and course, and it is more simple and convenient, namely, at first, assess the material readiness roughly, then assess the entries detailed of this level and afford corresponding evidences, at last, confirm the material readiness. In the course of assessment, the technic decomposing and crux technic elements recognizing are not requisite. The characteristic of material readiness assessment is decided by material development rule. © (2011) Trans Tech Publications. Source

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