7A09超高强铝合金表面强化实验研究

Experimental Study of 7A09 Ultra-high Strength Al Alloy Treated by Surface Strengthening

利用气动式喷丸机对7A09超高强铝合金试样进行喷丸强化,对喷丸强化前后试样小孔两侧残余应力分布进行测试,探讨了喷丸时间对7A09铝合金疲劳寿命的影响,分析机械喷丸强化前后铝合金试样疲劳断口。结果表明,机械喷丸强化后,7A09超高强铝合金表层分布高幅值残余压应力,表层残余压应力分布显著地降低了疲劳裂纹扩展速率,疲劳寿命明显提高;通过扫描疲劳断口,发现未处理试样的疲劳裂纹源位于孔壁上表面的尖角处,而机械喷丸强化试样的裂纹源逐渐转移到强化层以内,在最终断裂区内分布大量韧窝,且韧窝形态随喷丸时间的延长而增大,并且韧窝尺寸更深,说明机械喷丸改善了最终断裂区的塑性。

The pneumatic shot peening equipment was used to perform shot peening process on 7A09 samples with different peening time, the residual stress distribution around the hole before and after shot peening processing was studied, the effects of shot peening on fatigue life were discussed, and the inhibitory effects of shot peening on fatigue crack growth rate were analyzed, the fatigue fracture morphology characteristics after shot peening were observed. The results show that, compressive residual stress is introduced into the surface of samples by shot peening, which effectively decreases fatigue crack rate. By observing the fracture morphology, the fatigue crack initiation is at sharp comer on the surface before treating, which moves inside shot peening layer after shot peening, the dimples at fracture stage become larger and deeper after shot peening, which implies that shot peening can improve plasticity of 7A09.