Recrystallization Behavior Of GH4169Superalloy Under Pulsing Current

Due to its magnificent high temperature strength and remarkable overall performance, superalloy keeps an important position, which can not be replaced in the fields of aviation, aerospace and many other industries. With the requirement of the performance and quality constantly improving, the degree of alloying of superalloy is also increased, so many harsh problems such as high resistance of deformation, high temperature of recrystallization and narrow temperature range of hotwork occured. Searching for new plastic processing theories and techniques to solve these difficult problems of superalloy is particularly important.As a form of energy instantaneous inputted, a lot of achievements have been obtained in the research of plastic working of some metallic materials such as magnesium alloy, titanium alloy and stainless steel utilizing the electroplastic effect of pulsing current. The temperature of recrystallization of metallic materials can be declined by pulsing current, which is exactly the key factor for enlarging the temperature range of hotwork of hard-deformation superalloy. So far, there is no precedent study on recrystallization behavior of hard-deformation superalloy under pulsing current, which is the premise and foundation for solving the problem of hard-deformation of superalloy making use of pulsing current.Therefore the annealing tests under pulsing current of GH4169alloy were carried out, the variations of initial temperature of recrystallization and recrystallization activation energy of GH4169alloy under pulsing current with different parameters were investigated, and the influence mechanism of pulse current on the static recrystallization behavior of GH4169alloy was researched in this paper. In addition, the electropulsing with different parameters acompanied tensile tests of GH4169alloy at800℃were carried out, and the influence of pulse current on the dynamic recrystallization behavior of GH4169alloy was investigated in present study.Based on present research, it is found that pulse current can reduce the initial temperature of recrystallization of GH4169alloy remarkably, and the extent of decline raises with the growth of pulse frequency, current density and pulse width. Pulse current can also lower the recrystallization activation energy of GH4169alloy. The apparent recrystallization activation energy of alloy is342.71kJ/mol under pulsing current (4kA、20Hz、30μs) treating which was declined for39.8%comparing to577.19kJ/mol under normal annealing. The recrystallization mechanism and process of GH4169alloy is both closely related to the precipitation of δ phase. When δ phase dispersed in grain boundry or the size of δ phase was small, recrystallization was advanced mainly through the migration of original grain boundry. While the opposite situation of δ phase precipitation occurred, recrystallization of alloy was pushed forward primarily through nucleation newly. Recrystallization of GH4169alloy was influenced comprehensively by pulsing current through the precipitation of8phase and the nucleation and growth of recrystal grain.The sharply decline of deformation resistance of GH4169alloy in elevated temperature tensile at800℃due to pulsing current was related to the improvement of dislocation movement owing to pulse current(electroplastic effect). While the raise of plasticity of alloy under pulse current attributed to both the electroplastic effect and the advance effect of pulse current on dynamic recrystallization behavior. The dynamic recrystallization process of alloy can be promoted and the critical deflection of dynamic recrystallization can be bring down by pulse current with the current intensity raising.