30% HNO₃ 对 2195 铝锂合金预腐蚀疲劳特性研究

To simulate the material and application characteristics of liquid-missile propellant tanks, fatigue tests were carried out after pre-corrosion in 30% HNO₃ for different hours. Effects of pre-corrosion on fatigue properties were investigated by scanning electron microscopy (SEM), transmission electron microscope (TEM), and electron backscatter detector (EBSD) methods. The results show that the surface morphology after corrosion is mainly composed of intergranular corrosion and pitting. Stripped corrosion chains are produced along the rolling direction, which are related with corroded long grain boundaries and intermetallic particles. The fatigue limit values of pre-corroded specimens are lower than those of the uncorroded specimens. The fatigue limit of 16 h corroded specimens is the highest, while the limit of 24 h corroded specimens declines to zero. The fatigue cycles under median stress amplitudes of 210 MPa, 280 MPa and 330 MPa, higher than those of uncorroded specimens, and the increase of 16 h corroded specimens is the most obvious. The enhancement of fatigue cycles attributes to the elimination of microcracks, pores and the improvement of surface roughness through pre-corrosion, which reduces the stress concentration and retards the crack initiation.