采用挤压棒直接冷挤压的方法,对比分析了超高强7055-T7751铝合金厚板带孔试样孔挤压前后的疲劳寿命;通过透射电镜观察、扫描电镜观察以及X射线应力分析等方法,研究了7055-T7751厚板带孔试样的疲劳断口形貌特征、微观组织变化以及孔壁表层的残余应力场.结果表明,采用3%～5%的挤压量对7055-T7751厚板进行孔挤压强化可取得较好的疲劳强化效果,试件的疲劳寿命提高了33倍以上;孔挤压后的强化层深度约为7mm,最大残余应力出现在距孔边约0.5mm处,应力值为-554MPa.强化层内形成的位错胞状结构和残余压应力可有效延缓疲劳裂纹的扩展速率,从而提高试件的疲劳寿命.
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