The contrasting roles of creep and stress relaxation in the time-dependent deformation during in-situ cooling of a nickel-base single crystal superalloy

An in situ scanning electron microscope (SEM) tensile test for Ni-based single-crystal superalloy was carried out at 1000 °C. The stress displacement was obtained, and the yield strength and tensile strength of the superalloy were 699 MPa and 826 MPa, respectively. The crack propagation process, consisting of Model I crack and crystallographic shearing crack, was determined. More interestingly, the crack propagation path and rate affected by eutectics was directly observed and counted. Results show that the coalescence of the primary crack and second microcrack at the interface of a γ/γ′ matrix and eutectics would make the crack propagation rate increase from 0.3 μm/s to 0.4 μm/s. On the other hand, crack deflection decreased the rate to 0.05 μm/s. Moreover, movement of dislocations in front of the crack was also analyzed to explain the different crack propagation behavior in the superalloy.

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Tensile behavior of nickel-base single-crystal superalloy DD6

Materials Science and Engineering A ◽

10.1016/j.msea.2015.03.125 ◽

2015 ◽

Vol 636 ◽

pp. 608-612 ◽

Cited By ~ 24

Author(s):

Xinhong Xiong ◽

Dunmiao Quan ◽

Pengdan Dai ◽

Zhiping Wang ◽

Qiaoxin Zhang ◽

...

Keyword(s):

Single Crystal ◽

Tensile Behavior ◽

Single Crystal Superalloy ◽

Nickel Base

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Effect of misorientation on the fatigue life of nickel-base single crystal superalloy DD5 at 980°C

International Journal of Fatigue ◽

10.1016/j.ijfatigue.2021.106479 ◽

2021 ◽

pp. 106479

Author(s):

Piao Li ◽

Wen Jiang ◽

Shao-Shi Rui ◽

Wei-xing Yao ◽

Hui-ji Shi ◽

...

Keyword(s):

Fatigue Life ◽

Single Crystal ◽

Single Crystal Superalloy ◽

Nickel Base

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Creep Behavior of a 4.5% Re Nickel-Base Single Crystal Superalloy at High Temperature

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.750.139 ◽

2015 ◽

Vol 750 ◽

pp. 139-144 ◽

Cited By ~ 1

Author(s):

De Long Shu ◽

Su Gui Tian ◽

Xin Ding ◽

Jing Wu ◽

Qiu Yang Li ◽

...

Keyword(s):

Heat Treatment ◽

High Temperature ◽

Single Crystal ◽

Deformation Mechanism ◽

Creep Property ◽

Single Crystal Superalloy ◽

Micro Cracks ◽

Initiation And Propagation ◽

Temperature Ranges ◽

Nickel Base

By means of heat treatment and creep property measurement, an investigation has made into the creep behaviors of a containing 4.5% Re nickel-base single crystal superalloy at high temperature. Results show that the elements W, Mo and Re are enriched in the dendrite arm regions, the elements Al, Ta, Cr and Co are enriched in the inter-dendrite region, and the segregation extent of the elements may be obviously reduced by means of heat treatment at high temperature. In the temperature ranges of 1070--1100 °C, the 4.5% Re single crystal nickel-based superallloy displays a better creep resistance and longer creep life. The deformation mechanism of the alloy during steady state creep is dislocations slipping in the γ matrix and climbing over the rafted γ′ phase. In the later stage of creep, the deformation mechanism of alloy is dislocations slipping in the γ matrix, and shearing into the rafted γ′ phase, which may promote the initiation and propagation of the micro-cracks at the interfaces of γ/γ′ phases up to the occurrence of creep fracture.

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