Effects of solid-solution temperature on heat-treated microstructure and mechanical properties of a novel nickel-base wrought superalloy with high γ'content
It was studied that the effects of solution temperature on heat-treated microstructure and resultant mechanical properties of a novel nickel based superalloy with a high content of γ'precipitates by means of optical microscopy(OM),field emission scanning electron microscopy(FE-SEM)and mechanical experiments.The as-received hot-rolled microstructure undergoes static recrystallization during the solid-solution treatment completely.The recrystallized grains remain fine uniformly at 1120 and 1130℃,but become significantly coarser with a poor uniformity at 1150 and 1190℃.As the solid-solution temperature rises,the content of primary γ'precipitates at grain boundaries decreases;while the number of secondary γ'precipitates increases and their size decreases,until it exceeds the γ'solvus(about 1134.3℃).It is indicated that the mechanical properties of this alloy are jointly determined by the size of γ grains and the content and distribution of γ'precipitates within γ grains.The tensile strength both at room temperature and 850℃increases first and then decreases with the increase of solid-solution temperature.Compared with that of coarse-grained microstructure,the tensile plasticity of fine-microstructure is high at room temperature but poor at 850℃.The coarser the recrystallized γ grains,the longer the stress-rupture lifetime and the higher the stress-rupture plasticity under 850℃/350MPa.The heat-treated microstructure with a solid-solution temperature of 1130℃obtains a higher high-cycle fatigue lifetime at 850℃.
Ni-base wrought superalloyhigh content of γ'precipitatesolid-solution temperaturemicrostructuremechanical property
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