Effect Of δ-phase On The Microstructural Evolution And Properties Of GH4169 Alloy

GH4169 al oy has excel ent tensile,creep,and corrosion resisitance properties in high-temperature environments.It is well known thatγ’,γ"andδ-phases are the major precipitates of the GH4169 al oy,and the good performance is related to the amount of the phase,size,morphology and distribution of precipitates.Changing the composition of the al oy has gradually become an important way to meet the stringent environmental requirements.Besides,deformation is an important means of optimizing the microstructure and improving the properties in the nickel-based al oy.Previous investigations mainly focus on the effect of cold rolling onδ-phase.However,there are few literatures to study the effect of cold rolling on theγ″-phase evolution of GH4169al oy.In this work,the effects of cold rolling andδ-phase on the coarsening behavior ofγ″-phase in GH4169 aloy were investigated by optical microscopy（OM）,scanning electron microscopy（SEM）.And the influence ofδ-phase on the microstructure and properties of GH4169 al oy was quantitatively analyzed by electronic creep testing machine.The following conclusions can be reached as follows:（1）The pre-precipitatedδ-phase retards the growth of theγ″-phase without affecting the final size and content,and cold rolling treatment substantially reduces theγ″-phase content until theγ″-phase becomes invisible with prolonged aging time.（2）The coarsening behavior of theγ″-phase follows the Lifshita-Slyozov-Wagne diffusion growth theory,and the thus-obtained activation energy during the growth of theγ″-phase in normal aged treatment and primaryδ-phase contain are 292 kJ·mol^-1and 302 kJ·mol^-1,respectively.（3）Theδ-phase content in the microstructure of the explored aloy increases during creep process,and part ofδ-phases change from needle-like or lamel ar to spherical particles which can prolongs the creep life by hindering the movement of dislocation in GH4169 alloy.（4）Both the creep rupture life and fracture type of the GH4169 superalloy would be considerably affected byδ-phase amount.As theδ-phase amount is up to 4.7%,the al oy exhibits the longest creep rupture life of 936 h,accompanying with intergranular and transgranular hybrid fracture pattern at 650°C/630MPa.