GH4169高温合金热机械疲劳循环损伤机理及数值模拟

Thermo-Mechanical Fatigue Cycle Damage Mechanism and Numerical Simulation of GH4169 Superalloy

在0.6%和0.8%应变幅下,对镍基高温合金GH4169开展了温度循环为350~650℃的同相位(IP)和反相位(OP)热机械疲劳(TMF)实验。分析了TMF迟滞回线、循环应力响应行为、疲劳裂纹萌生和扩展行为以及疲劳寿命。实验结果表明,TMF应力-应变曲线呈现拉压不对称状态,高温半周有明显循环软化现象,相同应变幅状态下TMF寿命比峰值温度下的等温低周疲劳(LCF)寿命更短,且应变幅增大导致循环变形增大并降低疲劳寿命。结合断口分析发现,IP TMF裂纹表现为沿晶断裂,而OP TMF裂纹表现为穿晶断裂。最后使用Chaboche黏塑性模型模拟了TMF循环变形行为,模拟与实验结果较为吻合,能够反映TMF基本特征。

Under complex cyclic force/thermal multifield coupled service conditions,one of the most common failure types of aeroengine turbine disks is thermo-mechanical fatigue(TMF) failure.In metallurgy,petrochemicals,nuclear energy,aviation,and other industries,the GH4169 superalloy is frequently used.To further enrich the fatigue performance data of this alloy,in-phase(IP) and out-of-phase(OP)TMF tests were conducted on the nickel-based superalloy GH4169 at 0.6% and 0.8% strain amplitudes with temperature cycling from 350oC to 650oC.The TMF hysteresis loops,cyclic stress response behavior,fatigue crack initiation,propagation behavior,and fatigue life were analyzed.The experimental results show that the TMF stress-strain curves show tensile-compression stress asymmetry,and there is obvious cyclic softening in the high-temperature half-cycle.The TMF life is shorter than the isothermal fatigue life at the peak temperature under the same strain amplitude.Moreover,the increase of strain amplitude leads to the increase of cyclic deformation and reduces the fatigue life.The fracture analysis and the results show that the OP TMF cracks display transgranular fracture,while the IP TMF cracks show intergranular fracture.Finally,the TMF cyclic deformation behavior was simulated using the Chaboche viscoplastic model,and the simulation results were consistent with the experimental results,reflecting the basic characteristics of TMF.