【作者】 刘杨； 王磊； 蔡文良； 胥国华； 赵光普；

【Author】 Liu Yang;Wang Lei;Cai Wenliang;Xu Guohua;Zhao Guangpu;Key Laboratory for Anisotropy and Texture of Materials,Ministry of Education,Northeastern University;High Tenperature Material Research Institute,Central Iron and Steel Research Institute;

【机构】 东北大学材料各向异性与织构教育部重点实验室； 钢铁研究总院高温材料研究所；

【摘要】 研究了长期服役过程中的显微组织演化对航空发动机涡轮盘用GH4169合金的疲劳裂纹扩展行为的影响规律,揭示了合金服役过程中组织劣化对其疲劳裂纹扩展不同阶段的裂纹扩展路径及断裂行为的作用机制。结果表明,与标准热处理的相比,GH4169合金经650℃时效后,疲劳裂纹扩展速率疲劳裂纹扩展速率略有增加,但在不同阶段的变化规律各异。在Paris区,疲劳裂纹扩展速率基本无变化,在近门槛区与快速扩展区,随时效时间的延长,疲劳裂纹扩展速率增加较为明显。合金经750℃长期时效后,随时效时间的延长,疲劳裂纹扩展速率显著增加,而且,疲劳裂纹扩展的门槛值明显降低。在相同时效时间条件下,与650℃相比,GH4169合金经750℃长期时效后的疲劳裂纹扩展速率明显增加。GH4169合金经650℃长期时效后,γ′相和γ″相的粗化,降低了合金的强度;位错由切过方式变为绕过方式通过强化相,断口表面粗糙度降低,弱化了裂纹闭合效应,疲劳裂纹扩展抗力降低,裂纹扩展速率增加。GH4169合金经750℃长期时效后,大量γ″相向长针状δ相的转化,大大降低了合金强度;长针状的δ相阻碍位错滑移,造成强烈的应力集中,成为裂纹扩展的主要路径,弱化了裂纹闭合效应与裂纹尖端屏蔽效应,疲劳裂纹扩展抗力显著降低,裂纹扩展速率显著增加。裂纹闭合效应的主要决定因素为断口表面粗糙度,裂纹尖端应力屏蔽效应则主要由裂纹分支引起。更多还原

【Abstract】 The effects of microstructure evolution during long-term service on the fatigue crack propagation behavior of GH4169 superalloy used for turbine disk of aviation engine were studied.The mechanism of the effect of microstructure degradation on the fatigue crack propagation path at different stages and fracture behavior of the alloy during service was clarified.The results showed that the fatigue crack propagation rate increased slightly of the alloy after aging at 650 ℃compared with that of the standard heat treatment,but the variation of the fatigue crack propagation was different at different stages.In the Paris region,the fatigue crack propagation rate was almost unchanged,and it increased obviously with the increase of the aging time in the near-threshold region and fast propagation region.The fatigue crack propagation rate increased and the threshold value of fatigue crack propagation decreased significantly with increasing aging time of the alloy after long-term aging at 750 ℃.The fatigue crack propagation rate increased more obviously of the alloy after aging at 750 ℃ compared with that at 650 ℃ for the same aging time.The coarsening of the y and γ " phases reduced the strength of the alloy after aging at650℃.The dislocations motion changed from cutting to bypassing through the strengthening phases.The crack closure effect was weakened by the reducing fracture surface roughness,which decreased the fatigue crack propagation resistance and increased the fatigue crack propagation rate.While in the alloy after aging at 750 ℃,the transformation of a large number of γ" phases to long needle like 8 phases decreased the strength of the alloy.The 8 phase blocked the dislocations slipping,caused the stress concentration and became the main path for the fatigue crack propagation.As a result,the crack closure effect and the crack tip shielding effect were weakened,the fatigue crack propagation resistance was significantly reduced and the fatigue crack propagation rate increased significantly.The main determining factor of the crack closure effect is the fracture surface roughness and the stress shielding effect of the crack tip is mainly caused by the crack branching.更多还原