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研究2A97铝锂合金的疲劳裂纹萌生及早期扩展行为。在室温条件下,采用光滑试样进行疲劳测试,其中最大应力为恒定值,应力比R为0.1,频率f为40 Hz。利用金相显微镜、透射电镜、扫描电镜及电子背散射衍射等手段对合金的微观组织进行分析,研究合金的疲劳裂纹萌生及早期扩展行为与其微观组织的关系。结果表明:2A97合金的疲劳裂纹主要萌生于试样表面的杂质相和粗大第二相处;其疲劳裂纹的早期扩展行为主要受晶粒结构与位错或滑移带共同作用的影响。当相邻晶粒的错配度接近于其晶内的最优滑移面的位向差时,大角度晶界强烈阻碍滑移带的运动,从而导致裂纹分叉和偏折。
Study on Fatigue Crack Initiation and Early Expansion of 2A97 Al-Li Alloy. At room temperature, the fatigue test was performed on smooth specimens of which the maximum stress was constant, the stress ratio R was 0.1 and the frequency f was 40 Hz. The microstructure of the alloy was analyzed by metallographic microscope, transmission electron microscopy, scanning electron microscopy and electron backscatter diffraction to study the relationship between fatigue crack initiation and early extension behavior of the alloy and its microstructure. The results show that the fatigue crack initiation of 2A97 alloy mainly occurs at the impurity phase and the coarse second phase of the sample surface. The early fatigue propagation of the fatigue crack is mainly affected by the combination of grain structure and dislocation or slip band. When the misfit of adjacent grains is close to that of the optimal slip plane in its crystal, the large-angle grain boundaries strongly impede the movement of the slip band, causing the furcation and deflection of the crack.