Toward an understanding of dwell fatigue damage mechanism of bimodal Ti-6Al-4V alloys  

作　　者：L.R.Zeng L.M.Lei X.M.Luo G.P.Zhang 

机构地区：[1]Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China [2]School of Mechanical Engineering,Chengdu University,Chengdu 610106,China [3]AECC Shanghai Commercial Aircraft Engine Manufacturing Co.,Ltd.,Shanghai 201306,China

出　　处：《Journal of Materials Science & Technology》2022年第13期244-255,共12页材料科学技术（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Nos.51771207 and 52171128);the Fundamental Research Project of Shenyang National Laboratory for Materials Science(No.L2019R18)。

摘　　要：Dwell fatigue effect is a long-standing problem threatening the long-term service reliability for fan blades and fan disks of an aircraft engine.To understand the basic mechanism of dwell fatigue damage,pure fatigue and 60 s dwell fatigue properties of bimodal Ti-6Al-4V alloys with different volume fractions of the primaryα(α_(p))phase were examined comparatively.The results showed that both pure fatigue and dwell fatigue life decreased with increasing the volume fraction of theα_(p)phase and the dwell fatigue life was lower than the pure fatigue one.The quasi-in-situ test results and the quantitative characterization of damage behaviors of the local microstructure units defined by theα_(p)-secondaryα(α_(s))combination reveal that theα_(s)phase close to theα_(p)phase with extensively slip activities was gradually damaged under dwell fatigue loading,while that under pure fatigue loading was undamaged,demonstrating that the dwell loading induced the damage of theα_(s)phase,and further reduced the fatigue life.A stress relaxation-based model is proposed to describe the physical mechanism on dwell fatigue damage of the bimodal Ti-6Al-4V alloy,i.e.the elastic deformation of theα_(s)phase caused by the strain incompatibility would be gradually transformed into plastic deformation during the dwell stage,and thus promotes fatigue damage.The model provides new insights into the microscopic process of stress/strain transfer between the soft and hard microstructure units under dwell fatigue loading.

关 键 词：Dwell effect Fatigue damage Stress relaxation Volume fraction of primaryαphase Quasi-in-situ testing 

分 类 号：V252[一般工业技术—材料科学与工程] TG146.23[航空宇航科学与技术—航空宇航制造工程]