采用孔挤压方法对含孔的7A85铝合金锻件进行了强化, 对比分析了孔挤压前后试样的疲劳寿命; 通过扫描电镜、透射电镜以及X射线应力仪等研究了挤压前后试样的疲劳断口形貌、显微组织变化以及孔表层的残余应力场。结果表明: 采用5.3%的挤压过盈量可达到最佳强化效果, 其疲劳寿命是挤压强化前的11倍; 孔挤压强化后, 试样在强化层处产生位错缠结及残余压应力, 可有效延缓疲劳裂纹的扩展, 从而提高试样的疲劳寿命, 压应力层深度约为4.7 mm, 最大残余压应力出现在距孔边约1 mm处, 其值为-319 MPa。

Hole expansion was employed to strengthen 7A85 aluminum alloy forging with holes. The fatigue lives of specimens before and after hole expansion were analyzed by comparison. The fatigue fracture, microstructure and residual stresses before and after hole expansion were studied by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that the specimens with the shrink value of 5.3% obtained the best effect of strengthening, whose fatigue life was 11 times as long as that before hole expansion. The residual compressive stress and dislocation cell structure were found in the strengthened layer after hole expansion, which can retard the fatigue crack growth rate, and then prolongs the whole fatigue life of the specimen. The depth of strengthening layer was about 4.7 mm, and the maximum residual compressive stress of -319 MPa was observed where was 1 mm away from the border of holes.