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Effect of Thermal Exposure on the Micro-structure and Performance of Surface Pre-deformed Single-crystal Superalloy
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AECC Beijing Institute of Aeronautical Materials

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    Abstract:

    [001] oriented DD11 single-crystal superalloy (SC) was shot-peened perpendicular to [001] to induce pre-deformation. Pre-deformed micro-structure was investigated using elecron backscatter diffraction (EBSD), scanning electron microscopy (SEM) and micro-hardness tester (HT). After subsequent thermal exposure (TE), the effect of the temperature and pre-deformation degree on surface structure was researched by SEM and HT, moreover, high-temperature fatigue performance after peening-exposure was tested. The results show that after pre-deformation, [110] and [111] oriented subgrains were observed on the surface, and that surface strain hardening effect occured. The greater the deformation degree was, the larger the subgrain orientation angle, the depth of the rotating subgrain layer and the hardening effect were. With the increase of exposure temperature, the pre-deformed surface micro-structure showed a relaxion of micro-hardness and a dynamic recovery process of spheroidization, fragmentation-discontinuous cellular organization and continuous cellular organization. Furthermore, the greater the deformation degree was, the lower temperature the recovery process occured at. However, the recrystallization was not observed at the condition of shot peening and 1060℃/2h. Compared with grinding and TE, the 1060℃ fatigue cycles increased while peening and TE. For fatigue condition 1060℃/350MPa/r=-1/axic, the main source of fatigue is sprouting inside, while secondary source is born on the surface.

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[Wang Xin, Ai Yingjun, Tang Zhihui, Liu Chenguang, Zhao Zhenye, Li Chunzhi. Effect of Thermal Exposure on the Micro-structure and Performance of Surface Pre-deformed Single-crystal Superalloy[J]. Rare Metal Materials and Engineering,2019,48(2):573~579.]
DOI:10.12442/j. issn.1002-185X.20170598

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History
  • Received:July 06,2017
  • Revised:August 26,2017
  • Adopted:September 12,2017
  • Online: March 15,2019
  • Published: