摘要
采用光学显微镜、扫描电镜、扫描透射电镜和电子背散射衍射等分析方法研究了7020铝合金型材疲劳行为及微观机制。结果表明在应力比R为0、疲劳极限寿命取10^(7)周次时,合金疲劳强度为232.9 MPa。疲劳裂纹尖端应力强度因子ΔK=8 MPa·m^(1/2)时,裂纹扩展速率约为6.44×10^(-5)mm/cycle。合金中尺寸在3~12μm的粗大难熔结晶相不仅易成为疲劳裂纹源,也会加速疲劳裂纹扩展。在未再结晶区域,疲劳裂纹主要以穿晶方式扩展。当裂纹扩展到易滑移平面取向差较大的再结晶小晶粒时,裂纹易沿其大角度晶界快速扩展。合金再结晶程度及其对应的大角度晶界占比越低时,疲劳裂纹扩展路径越曲折,扩展速率越慢。
The effect of microstructure on fatigue behavior of 7020 aluminum alloy profile was investigated by optical microscopy,scanning electron microscopy,scanning transmission electron microscopy and electron back scattering diffraction technique.The results show that the fatigue strength of the alloy is 232.9 MPa at 10^(7)cycles of loading,under the stress ratio R of 0.The fatigue crack growth rate is about 6.44×10^(-5)mm/cycle atΔK of 8 MPa·m^(1/2).The coarse high-melting intermetallic compounds with a size of 3μm to 12μm in the alloy not only easily become the initiation of fatigue crack,but also accelerate fatigue crack growth.In the unrecrystallized area,the fatigue crack growth of the alloy mainly occurs by a transgranular mechanism.When the adjacent grains are small equiaxed recrystallized grains with high misorientation,fatigue cracks would propagate rapidly along the grain boundaries.The lower the proportion of recrystallization and its corresponding high-angle grain boundaries,the more tortuous of the fatigue crack propagation path.Under these conditions,the fatigue crack of the alloy propagates slowly.
作者
单朝军
刘胜胆
张新明
叶凌英
李亦然
唐建国
邓运来
Shan Zhaojun;Liu Shengdan;Zhang Xinming;Ye Lingying;Li Yiran;Tang Jianguo;Deng Yunlai(School of Materials Science and Engineering,Central South University,Changsha 410083,China;Key Laboratory of Nonferrous Metal Materials Science and Engineering,Ministry of Education,Central South University,Changsha 410083,China;School of Civil Engineering,Harbin Institute of Technology,Harbin 150001,China)
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2021年第5期1803-1811,共9页
Rare Metal Materials and Engineering
基金
国家重点研发计划(2016YFB0300901)。
