微量Hf对大角度晶界含Re双晶合金高温持久性能的影响

Effects of minor Hf on high temperature stress rupture properties of high angle grain boundary in a Re-containing Ni-based bicrystal superalloy

采用籽晶法制备含有大角度晶界(约20°)的双晶试板,通过分析不同Hf含量(质量分数:0%,0.4%)的含Re合金晶界处析出相、γ/γ′组织、晶界成分及1100℃/100MPa横向持久性能,研究Hf对晶界组织及高温力学性能的影响。结果表明:Hf显著提高了铸态合金大角度晶界处共晶和碳化物体积分数;热处理后,Hf显著抑制了晶界胞状再结晶组织的形成,含Hf合金的1100℃/100MPa横向持久寿命均显著提高。晶界持久性能与晶界析出相种类、形貌、含量和成分密切相关,而Hf元素在晶界未发现显著的偏聚。本研究对先进镍基单晶合金中晶界缺陷的评价及Hf元素晶界强化作用机制的认识具有一定的指导意义。

Two bicrystal specimens containing high angle grain boundary(about 20 degrees)were prepared by seed crystal method.The effect of Hf on the as-cast,heat-treated grain boundary micro structure,composition and stress rupture properties under 1100℃/100MPa was investigated in N--based single crystal superalloy contained Re with different contents of Hf(mass fraction:0%,0.4%).The results show that Hf addition results in the increase of the volume fraction of(γ+γ′)eutectic and MC along the grain boundary.The volume fraction of cellular recrystallization microstructure is significantly decreased after heat treatment with Hf addition.The transverse stress rupture life is observed to increase significantly under 1100℃/100MPa in the H-containing alloy.The stress rupture properties are closely related to the type,morphology,content and composition of the precipitation phase along grain boundary,but the obvious segregation of Hf s not observed.This study can be helpful for the understanding of Hf?s role of strengthening mechanism in grain boundary in advanced Ni-based single crystal superalloy.