喷丸处理对7A85-T7452铝合金锻件疲劳性能的影响

Influence of shot peening on the fatigue property of 7A85-T7452 aluminum alloy forging

研究不同喷丸强度对7A85-T7452铝合金锻件高周疲劳性能的影响,对比喷丸处理前后1×10^(7)疲劳寿命条件下的疲劳强度,利用扫描电镜(SEM)和透射电镜(TEM)观察了疲劳断口的形貌特征以及强化层微观组织的变化,用X射线(XRD)检测了强化层残余应力的分布。结果表明:喷丸后7A85铝合金试样的疲劳寿命是未喷丸的7.3倍,疲劳强度提高18%。喷丸在材料表面形成了厚度约为0.09 mm的残余压应力层,最大压应力为-231 MPa,该强化层平衡部分外加载荷中的瞬时拉应力,残余压应力层内的高密度位错可以阻碍位错的滑移,导致晶内位错迁移困难,从而阻碍了疲劳裂纹的萌生和扩展。

The influence of different shot peening on the high cycle fatigue property of 7A85-T7452 aluminum alloy forging was studied.The fatigue strength for 1×10^(7) fatigue life before and after the shot peening treatment was compared.The scanning electron microscope(SEM)and transmission electron microscope(TEM)were used to observe morphological features of fatigue fracture as well as the microstructure changes of strengthening layers,while the X-ray(XRD)was used to detect the residual stress distribution in the strengthening layers.The results showed that the fatigue life of 7A85 aluminum alloy samples after shot peening was 7.3 times longer than that without shot peening,and the fatigue strength increased by 18%.A residual compressive stress layer with a thickness of about 0.09 mm was formed on the material surface by shot peening,with the maximum compressive stress reaching-231 MPa,which could balance the instantaneous tensile stress in some external loads.The high-density dislocations in the residual compressive stress layer could hinder the slip of dislocations,thus resulting in the difficulty of intragranular dislocation migration and impeding the initiation and propagation of fatigue cracks.