FGH4102粉末高温合金等温热模拟压缩试验及动态再结晶组织研究

本文研究了新型第四代粉末高温合金FGH4102在等温热模拟压缩过程中的组织演变,对γ′相在动态再结晶过程中的作用进行了探讨。结果表明,热等静压态合金在1060~1120℃温度范围变形时,热加工性能较好。1140℃变形后试样容易发生开裂,合金热加工性能较差。合金在γ+γ′两相区变形时均发生了不同程度的动态再结晶,再结晶晶粒尺寸远小于热等静压态的晶粒尺寸。变形过程中,尺寸较大的γ′相起到促进动态再结晶的作用。变形参数对动态再结晶的影响非常显著。低温高应变速率变形时,γ′相促进动态再结晶形核占主导地位,再结晶晶粒比较细小;高温低应变速率变形时,晶粒长大逐渐占据主导地位,再结晶晶粒尺寸较大。

Isothermal compression test and dynamic recrystallization of the powder metallurgy superalloy FGH4102

Nickel-based powder metallurgy(PM) superalloys were widely used to manufacture the components in gas turbine engines owing to their outstanding mechanical properties at extremely high temperatures.In order to design a new generation aircraft engine with a higher thrust-weight ratio and satisfy the performance requirements,a fourth generation PM superalloy has been studying worldwide.The alloy FGH4102 in this study was a newly designed fourth generation PM superalloy,which exhibited excellent high-temperature stress rupture and creep properties compared with the previous three generations’ PM superalloys,FGH4095,FGH4096,and FGH4098.This work aims to study the thermal deformation behavior of hot isostatic pressured(HIPed) alloy under different deformation conditions and provided a reference for subsequent extrusion and isothermal forging process parameter design.The hot deformation behavior of HIPed alloy FGH4102 was studied by using isothermal simulation compression experiments.The effects of different deformation conditions(strain rate,strain temperature,and strain variables) on the volume fraction and grain size of dynamic recrystallization were analyzed,and the role of γ ’phase in dynamic recrystallization was discussed.The results show that the dynamic recrystallization of HIPed alloy FGH4102 occurs in different degrees within the range of deformation parameters.When the strain exceeds the critical strain,dynamic recrystallization takes place first near the original grain boundary.With the increase of strain,dynamic recrystallization grains gradually replace original coarse grains,and the volume fraction of dynamic recrystallization keeps increasing.After low temperature and high strain rate deformation,the dynamic recrystallization of the alloy is sufficient,and the grain size becomes smaller than the previous.The increase of deformation temperature and strain rate decreases the nucleation rate of dynamic recrystallization and increases the grain size of recrystallization.After the deformation at 1 140 ℃,the grain grows significantly,which leads to the deterioration of the hot working property of the alloy,and the sample is prone to cracking.When deformed in the γ+γ′ two-phase region,the fine secondary γ′ phases dispersed in the matrix have an inhibitory effect on dynamic recrystallization.As the size of the initial γ′ phase increases,the inhibition of recrystallization is gradually weakened.As for the HIPed alloy FGH4102,the micron-sized γ′ phases can promote dynamic recrystallization during hot deformation.When deformed at low temperature and high strain rate,γ′ phases promote dynamic recrystallization nucleation,and recrystallized grains are relatively small.When deformed at high temperature and low strain rate,grain growth gradually dominates.Moreover,the recrystallized grain sizes are comparatively large.