孔挤压强化对2124铝合金疲劳寿命及微观组织的影响

Influence of Hole Cold Expansion on Microstructure and Fatigue Life of 2124 Aluminum Alloy

采用疲劳试验、透射电镜、扫描电镜及X射线衍射仪等方法研究了2124-T851铝合金厚板不同参数孔挤压强化后疲劳寿命与显微组织的变化。结果表明:孔挤压强化后试样的疲劳寿命先随挤压量的增大而升高,随后又迅速降低,挤压量为0.4 mm时疲劳寿命达到峰值,较未强化增加12.66倍;组织观察结果表明孔挤压强化后,在孔壁强化层内形成了位错胞状结构和残余压应力,并且随挤压量增大先迅速增加然后趋于平缓,强化层的形成可以有效延缓疲劳裂纹的扩展速率;同时,适当的孔挤压强化可改善表面粗糙度,降低裂纹萌生几率,从而提高材料的疲劳寿命。

The change of fatigue life and microstructure of 2124-T851 thick plate after cold expanded with different deformation was studied by fatigue test, TEM , SEM and X-ray diffraction apparatus. The results show that the fatigue life increases with the increase of expanded deformation until the maximum value is reached, and then decreased rapidly with the increase of expanded deformation. At 0.4 mm expanded deformation, fatigue life reach peak value, which is 12. 66 times of the non-cold-worked specimens. The microstructure research results show that the residual compressive stress and dislocation cell structure form around the cold-worked holes during the cold expansion, and increase quickly with the expanded deformation. The strengthened layer retarded the fatigue crack growth rate. The appropriate cold expanded deformation can improve the surface roughness of hole, and retard the initiation of fatigue crack, consequently improving the whole fatigue life.