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| 超声强化2D12铝合金疲劳断裂过程的微观分析 |
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回丽1,2, 杨林青1,2, 王磊1,2, 许良1,2, 周松1
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1.沈阳航空航天大学 航空制造工艺数字化国防重点学科实验室, 沈阳 110136;2.沈阳航空航天大学 机电工程学院, 沈阳 110136
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| 摘要: |
| 采用超声强化工艺对2D12铝合金进行表面处理，借助金相显微镜和扫描电镜，并结合原位跟踪测量裂纹长度的方法，对强化后的疲劳断裂行为进行了研究。结果表明，超声强化后2D12铝合金表面晶粒得到细化，疲劳源主要产生于试样表面，仅个别向内部转移，强化后疲劳寿命提升了约8倍。其原因一方面是强化过程在试样表面引入了残余压应力，由于裂纹扩展过程倾向于连接裂纹扩展路径上的缺陷，所以残余压应力的存在效降低了裂纹在两缺陷间的扩展速率；另一方面晶粒细化导致晶界密度增加，加强了对裂纹扩展的阻碍，从而有益于提高裂纹扩展寿命。 |
| 关键词: 超声强化 2D12铝合金 缺陷 疲劳裂纹 |
| DOI：10.11933/j.issn.1007-9289.2016.06.003 |
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| 基金项目:国家自然科学基金（51405309）；辽宁省自然科学基金（2015020183） |
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| Micro-analysis of Fatigue Behavior in Ultrasonic Strengthened 2D12 Aluminum Alloy |
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HUI Li1,2, YANG Lin-qing1,2, WANG Lei1,2, XU Liang1,2, ZHOU Song1
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1.Key Laboratory of Fundamental Science for National Defense of Aeronautical Digital Manufacturing Process, Shenyang Aerospace University, Shenyang 110136;2.College of Electromechanical Engineering, Shenyang Aerospace University, Shenyang 110136
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| Abstract: |
| The fatigue fracture behavior and post fracture surface of 2D12 aluminum alloy that was treated by ultrasonic strengthening technology were investigated by optical and scanning electron microscopic analysis in combination with the in situ crack length tracking method. The results show that the grain size on the surface of 2D12 aluminum alloy is refined after ultrasonic strengthening treatment. The fatigue sources are mainly generated on the surfaces, while several cracks initiated from the inside of the strengthened specimens. The fatigue life is enhanced to about 8 times that of the base material after being strengthened. The reason is that the residual compressive stress is introduced on the surface of the specimen due to the strengthening process which can reduce the crack propagation rate between two flaws, while the crack propagation process tends to connect the defects along the crack propagation path. On the other hand, grain refinement leads to an increase in grain boundary density, which can enhance the resistance to crack propagation and thus contribute to the improvement of crack propagation life. |
| Key words: ultrasonic strengthening 2D12 aluminum alloy defects fatigue crack |