喷丸强化与应力因素对2E12铝合金晶间腐蚀行为的影响

Influence of Shot Peening and Stress Factor on Intergranular Corrosion of 2E12 Aluminium Alloy

为有效控制2E12铝合金的晶间腐蚀失效行为,采用浸泡腐蚀试验、金相分析技术、扫描电镜分析技术和X射线衍射分析技术等研究了喷丸强化和应力因素对2E12-T3铝合金晶间腐蚀行为的影响规律,并探讨了作用机理。研究结果表明:2E12-T3铝合金具有很高的晶间腐蚀敏感性,拉应力会明显增强其敏感程度,而压应力则会降低其敏感性。采用合理的喷丸强化处理(喷丸强度取0.15 mmN,覆盖率取100%)能够明显降低2E12-T3铝合金的晶间腐蚀敏感性,因为喷丸在铝合金表面引入合理分布的残余压应力,同时使表层晶粒细化,铝合金的电化学活性降低,晶间的选择性腐蚀得到有效控制。然而,喷丸强度过高或喷丸覆盖率过大时,铝合金表面会存在较严重的脱层等损伤性破坏,反而会使2E12-T3铝合金的晶间腐蚀敏感程度提高。

In order to effectively control the intergranular corrosion（IGC） failure behavior of 2E12 aluminium alloy,the influence of shot peening（SP） and stress factor on the IGC behaviour of the alloy were investigated by means of immersion corrosion experiment,metallographic analysis,scanning electron microscopy（SEM） and X-ray diffraction analysis,etc.The results show that 2E12-T3 alloy is very sensitive to IGC.Tensile stress can increase IGC sensitivity,while compressive stress can decrease IGC sensitivity.The IGC sensitivity of 2E12-T3 alloy can be effectively decreased by proper shot peeing treatment（shot peening intensity is 0.15 mmN,coverage is 100%）.The electrochemical activity is low and selective corrosion in grain boundary is effectively controlled by SP with suitable distribution of residual compressive stress and refinement of grain in surface layer.However,the IGC sensitivity of 2E12-T3 alloy will increase when shot peeing intensity is too high or its coverage is too large because such serious damage as delamination may occur in the SP surface layer of the alloy.