【摘要】 利用光学显微镜、场发射扫描电镜及力学性能测试等手段,研究了不同组织特征对GH4720Li合金高温拉伸和持久性能的影响。结果表明:组织B(局部混晶+一次γ′相)的650℃抗拉强度和屈服强度与组织A(均匀细晶+一次γ′相)相比有所降低;随着混晶程度的提高,组织C(完全混晶+一次γ′相)的抗拉强度迅速下降,但组织C的抗拉强度远高于粗晶组织D(粗晶+无一次γ′相)。不同持久试验条件下,合金的高温变形机制不同:730℃/530MPa条件下,组织A和组织D持久寿命相当,但从组织B和组织C可以看出持久寿命随混晶所占百分比的增加而提高,高温低应力下的变形机制主要为晶界粘滞滑动;680℃/830 MPa条件下主要变形机制是晶内位错滑移,组织A和组织B的持久性能较好,持久寿命随着粗晶所占百分比的增加而降低,同时晶界滑移同样产生一定作用,使得以粗晶为主的混晶组织持久寿命的降幅不大。更多还原

【Abstract】 The effects of the mixed-grain microstructure on mechanical property of nickel-based superalloy GH4720 Li were studied by optical microscope(OM), field emission scanning electron microscope(FE-SEM) and series properties tests. The results show that the tensile strength and yield strength of structure B(partial mixed crystal+primarny γ′ phase) at 650 ℃ for specimens are reduced compared with those of structure A(uniform fine grain+primary γ′ phase). The tensile strength of structure C(completely mixed crystal+primary γ′ phase) drops rapidly with the increase of volume fraction of coarse grain. Furthmore, the deformation mechanism of superalloys at high temperature is not the same under different stress-rupture test conditions. Under the condition of 730 ℃/530 MPa, the stress-rupture life increases with the increase of the volume fraction of coarse grain for the reason that grain boundary sliding mechanism plays an important role. While the major deformation mechanisms is found to be dislocation gliding under 680 ℃/830 MPa. Therefore, the stress-rupture life decreases with the increase of the volume fraction of coarse grain. Under this condition, the specimens with local coarse grain and fine grain have the best stress-rupture property.Grain boundary sliding also have certain effect under the condition, which results in not obviously reduction of the stress-rupture life for specimens mainly with coarse grain.更多还原