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This research conducted a thermal compression deformation test on two GH4169 alloy samples with 5.40wt% and 5.21wt% Nb contents respectively, under deformation temperatures ranging from 900°C to 1030°C and the strain rates of 0.04s-1, 0.08s-1. Data from the deformation test were used to study the effects of deformation temperature and strain rate o...
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... cross section of the deformed sample is shown in Figure 1, as can be seen that the deformation and temperature of core area is higher than edge aera, and microstructure of the core aera can reflect the real state under high temperature. At 0.04 s-1 strain rate, 50% deformation, the volume fractions of the δ phases at the heart of the high-Nbcontent alloy (HNB) were about 17.8%, 16.6%, 14.3%, 7.6%, and 0.67% respectively; the volume fractions of the δ phases at the heart of the low Nb content alloy (LNB) were about 3.8%, 1.9%, 1.6%, 0.2%, 0%, respectively. ...
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In the present study, the nucleation of static recrystallization (SRX) in austenite after hot deformation is experimentally analyzed using a Ni-30 pct Fe model alloy. In agreement with the predictions by current models, nucleation rate exhibits a strong peak, early during SRX. Whereas such an early peak is explained by current models by the saturat...
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... For the specimen with the true strain of 1.20, it can be seen that the long needle-like δ phases are obviously bent, twisted and folded. This is because the large strain applied from the outside will result in the occurrence of a high-density dislocation area near the long needle-like δ phases, causing the deformation and fracture of the δ phases [42]. Meanwhile, a large quantity of dislocation around the long needlelike δ phases provides a fast path for the diffusion of Nb atoms, thereby accelerating the dissolution of the long needle-like δ phases during deformation [43,44]. ...
... For the specimen with the true strain of 1.20, it can be seen that the long needle-like δ phases are obviously bent, twisted and folded. This is because the large strain applied from the outside will result in the occurrence of a highdensity dislocation area near the long needle-like δ phases, causing the deformation and fracture of the δ phases [42]. Meanwhile, a large quantity of dislocation around the long needle-like δ phases provides a fast path for the diffusion of Nb atoms, thereby accelerating the dissolution of the long needle-like δ phases during deformation [43,44]. ...
This study aims to explore the effect of deformation parameters on microstructure evolution during the new two-stage annealing method composed of an aging treatment (AT) and a cooling recrystallization annealing treatment (CRT). Firstly, the hot compressive tests with diverse deformation parameters were finished for an initial aged deformed GH4169 superalloy. Then, the same two-stage annealing method was designed and carried out for the deformed samples. The results show that the deformation parameters mainly affect the grain microstructure during CRT by influencing the content, distribution and morphology of the δ phase after deformation. The reason for this is that there is an equilibrium of the content of the δ phase and Nb atom. When the deformation temperature is high, the complete dissolution behavior of the δ phase nuclei promotes the dispersion distribution of the δ phase with rodlike and needle-like shapes during AT. Thus, the fine and heterogeneous microstructure is obtained after annealing because the recrystallization nucleation is enhanced in those dispersed δ phases during CRT. However, when the retained content of δ phase nuclei is high after deformation, the clusters of intragranular δ phases will form during AT, resulting in the pinning of the motion for dislocation. The elimination of the mixed grain microstructure is slowed down due to the low static recrystallization (SRX) nucleation rate within the deformed grain.
