Abstract
The influence of electropulsing treatment (EPT) parameters on the static recrystallization (SRX) microstructure in a cold-deformed Ni-based superalloy was investigated. During EPT, both the volume fraction of SRX grains and the average grain size increased with the increasing EPT temperature, which was attributed to the thermal effect and athermal effect induced by EPT. The mobility of SRX grain boundaries was promoted at the higher temperature due to the thermal effect, while the nucleation rate would be increased by EPT through decreasing the thermodynamic barrier. The formation of parallel dislocations caused by electron wind force could also play an indirect role in promoting SRX process. Moreover, the volume fraction of SRX grains increased significantly with the extension of EPT time at 700 °C, while the EPT time had a trivial effect on the average grain size. In addition, the sufficient deformation was essential to the occurrence of SRX behavior during EPT, and the localized Joule heating effect could promote the SRX behavior in the samples with the larger strains. Besides that, the influence of twining and carbides on the SRX behaviors was also investigated.
Highlights
Ni-based superalloys have been widely applied in the aerospace field, because of their extraordinary mechanical properties and corrosion resistance under the critical and severe service conditions [1,2,3].With the rapid development of aerospace industry, the working conditions of Ni-based superalloys have become more and more severe, and the higher requirements for alloy properties are put forward [4]
Temperature, and the volume fraction of SRX grains reached around 99% after treating for 20 min at electropulsing treatment (EPT) had a positive effect on the precipitation and growth of carbides, which played an indirect role in 900 °C
The mobility of SRX grain boundaries was promoted at the higher temperature owing to the thermal effect, and the nucleation rate could be increased by EPT through decreasing the thermodynamic barrier
Summary
Ni-based superalloys have been widely applied in the aerospace field, because of their extraordinary mechanical properties and corrosion resistance under the critical and severe service conditions [1,2,3]. Due to the fact that Ni-based superalloys belong to crystalline materials, optimization of crystal structures is considered to be one of the most effective methods for strengthening Ni-based superalloys [5] In this case, grain refinement via recrystallization has become a commonly employed approach, and the equiaxed fine crystal structures induced by recrystallization can significantly contribute to the mechanical properties of Ni-based superalloy parts, such as turbine discs [3]. Further research on the recrystallization microstructure evolution of Ni-based superalloys during the deformation and heat treatment process is very important for improving their mechanical properties. Guo et al [14] studied the influence of EPT on the recrystallization behavior of cold-rolled Mg alloy ZK60 strips, and it was found that the nucleation rate and migration ability of grain boundaries were significantly promoted by EPT, leading to the acceleration of recrystallization behavior at the relatively low temperature. The underlying mechanisms were discussed in detail
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