Evolution of interfacial dislocation network during anisothermal high-temperature creep of a nickel-based superalloy

Abstract

The effect of thermal cycling creep on the dislocation networks at the c/c 0 interfaces in the MC2 superalloy is investigated. Tensile creep tests were performed under thermal cycling and isothermal conditions at low stress (80 MPa) and high temperature (1150°C). In these conditions c 0 rafts may dissolve and reprecipitate during thermal cycling creep. The difference between the effects of isothermal and thermal cycling conditions on the c/c 0 interface dislocation networks, characterized by transmission electron microscopy, is exposed, as well as their evolution during the cycle.

Effect of thermal exposure on the stress-rupture life and microstructure of a low Re-containing single crystal alloy

“…The dislocations lines are mainly in the slip directions (〈110〉 directions), seldom mismatch directions (〈001〉 directions) kind of dislocations are found in local area. Similar dislocation networks have also been observed under different creep conditions in others' works [11,12]. However, Zhang et al [8] studied the creep deformation of the modern superalloys with high Re content at 1100 1C/137 MPa, and the results show that the deposited slip dislocations on the γ/γ 0 interface have reoriented from the slip directions to the mismatch directions in TMS-138 superalloy after 60 h creep test.…”

High-temperature creep of single-crystal nickel-based superalloy: microstructural changes and effects of thermal cycling

“…Indeed the interfacial dislocation network does not appear to evolve along the thermal cycle [36]. During the temperature dwell of the thermal cycle (from C to A), we can note that the thickness of the rafts decreased and that the period of the structure increased which means that the small rafts formed during the cooling step were totally dissolved and that the larger ones began to dissolve slowly under the synergetic effect of temperature and plastic strain.…”

Measurement of the effective γ/γ′ lattice mismatch during high temperature creep of Ni-based single crystal superalloy

“…As an example, authors from a recent study have confused the γ/γ′ interfacial dislocation networks with the fine (tertiary) γ′ precipitation within the γ channels [50]. Finally, the last source of scatter considering SEM measurements may arise from the assumption that all the dislocations composing the γ/γ′ interfacial networks have a/2<110> type Burgers vector while it was already noticed that numerous dislocation reactions within the networks may lead to the creation of <100> type dislocation segments [26]. We however feel that since the density of such kind of dislocations within an interfacial network is much smaller than the one of <110> type dislocations, the average value of the effective lattice mismatch determined plotting the distributions of average dislocation spacings is hardly affected, even if <100> type dislocations are included within the distribution.…”

“…Several techniques are commonly used to measure the γ/γ′ effective lattice mismatch. They either involve room temperature X-ray diffraction (XRD) after creep deformation [3,[22][23][24] or post-mortem dislocation spacing measurement using Transmission Electron Microscopy (TEM) [15,16,18,21,23,25,26]. Most recent techniques allow a high resolution continuous measurement of δ ⊥ during a high temperature creep test performing XRD under synchrotron radiation [27][28][29][30][31][32][33], or a post-mortem measurement of the δ ⊥ distributions in the volume of the sample using high resolution Scanning Electron Microscopy (SEM) observations after specific chemical etching preparations [34,35].…”