腐蚀预损伤对铝合金小裂纹行为影响研究

Study on Per-corrosion Damage Effect on Behavior of Small Crack for Aluminum Alloy

研究了不同腐蚀预损伤对新型高强铝合金小裂纹行为的影响。小裂纹试验采用单边缺口拉伸试样(SENT),在试样半圆形缺口根部预制直径大小为100-300μm的单腐蚀坑,后在空气环境进行疲劳小裂纹实验,实验在R=0.5恒幅载荷下,采用复型法观测小裂纹的萌生及扩展情况。结果表明,与预腐蚀24h试样相比,预腐蚀240h试样产生的裂纹数量较少,裂纹萌生与扩展较快。预腐蚀240h试样裂纹绝大多数萌生于腐蚀坑处而预腐蚀24h试样并未出现类似特性。预腐蚀240h试样未显现明显的小裂纹效应,预腐蚀24h试样有较明显的小裂纹效应出现。文中还通过引入参数aT对腐蚀时间与小裂纹受微观组织影响程度的关系进行了描述。相较预腐蚀24h试样预腐蚀的240h试样的aT更短,小裂纹受微观组织影响也更小。

Single edge notch tension （SENT） specimens with 100-300mm diameter corrosion pit prefabricated at the root of the notch were used to investigate the behavior of fatigue small crack of new type of high strength aluminum alloy.Fatigue tests were carried out in air environment, under R=0.5 ratio loading. The initiation and growth of small crack were inspected by replica method.Experimental results show that there were less small cracks engender in the 240h pre-corrosion sample,compared with the 24h pre-corrosion sample. The small crack of tile 240h pre-corrosion sample appeared earlier and expanded faster.The most cracks of 240h pre-corrosion sample initiated from corrosion pit at the root surface of the semicircular edge notch yet this phenomenon didn＇t happen to the 24h pre-con＇osion sample. The small erack effect on the 24h pre-eorrosion sample was obvious but the 240h pre-corrosion sample was not.The parameter ar have been brought in to describing the relationship between the corrosion time and the influence of tbe microstructure on the small crack . The aT of the 240h pre-corrosion sample is shorter and the small crack effect of the 240h pre-eorrosion sample is weaker, compared with the 24h pre-corrosion sample.