【作者】 郝艳君；

【导师】 杨林；

【作者基本信息】 沈阳工业大学 ， 材料学， 2009， 硕士

【摘要】 综合性能优良的铝合金已广泛应用于不同的工业领域,对其力学性能尤其是疲劳性能的要求则越来越高。一般说来,疲劳失效是工程结构件的主要破坏形式之一,铝合金亦不例外,因此,研究铝合金的疲劳行为不仅具有理论价值,而且也具有一定的工程实用价值。铝合金的疲劳行为主要受其化学成分、显微组织等因素的影响。尽管人们已经对铝合金的疲劳行为进行了一定程度的研究,但关于不同热处理状态6061铝合金的低周疲劳问题的研究尚没有见到,因此,研究挤压态及热处理态6061铝合金低周疲劳行为,总结其疲劳变形的一般规律,确定相应的疲劳裂纹萌生和扩展模式,以期为提高6061铝合金的疲劳性能提供可靠的理论基础,同时对6061铝合金在工程实际中的可靠使用以及相关结构件的抗疲劳设计提供必要的理论依据具有重要意义。实验结果表明,不同热处理的挤压态6061铝合金在疲劳变形期间可以表现为循环应变硬化、循环稳定现象;时效处理后提高了挤压态6061铝合金循环变形抗力,而固溶处理则显著降低合金循环变形抗力;在较高的外加总应变幅下,固溶态6061铝合金的疲劳寿命最长,而时效态6061铝合金的疲劳寿命最短;当外加总应变幅较低时,挤压态6061铝合金的疲劳寿命高于经过热处理的合金的疲劳寿命;对于不同热处理的挤压态6061铝合金而言,其弹性应变幅、塑性应变幅与疲劳断裂时的载荷反向周次之间呈直线关系。疲劳断口形貌分析结果表明,在外加总应变控制的疲劳加载条件下,不同加工处理状态的挤压变形6061铝合金的疲劳裂纹均是以穿晶方式萌生于疲劳试样表面,并以穿晶方式扩展。更多还原

【Abstract】 Aluminum alloy has been widely applied to different industrial sectors for its excellent comprehensive properties, while its mechanical properties, especially fatigue performance are required increasingly high. Generally speaking, the fatigue failure is one of the major failure formats of engineering structural components, and the aluminum alloy is not an exception, and therefore the study of fatigue behavior of aluminum alloy not only has theoretical value, but also has some practical value in engineering.The fatigue behavior of aluminum alloy ware mainly influenced by their chemical composition, microstructure and other factors. Although the fatigue behavior of aluminum alloy has been researched in a certain degree, the research of different heat treatment states 6061 aluminum alloy on low-cycle fatigue is still not seen. Therefore, researching the low-cycle fatigue behavior of extruded and heat treatment state 6061aluminum alloy, summing up the general laws of the fatigue deformation, determining the corresponding fatigue crack initiation and expansion patterns, would provide a reliable theoretical basis for 6061 aluminum alloy to enhance the fatigue properties. At the same time, it is of great significance to provide the necessary theoretical basis for the use of 6061 aluminum alloy in engineering practice and the anti-fatigue design of relevant structural parts.The experimental results show that different heat treatment of extruded 6061 aluminum alloy can be expressed as the cyclic strain hardening, cyclic stabilization during the fatigue deformation; the aging treatment can increase the cyclic deformation resistance of the extruded 6061 alloy, but the solution treatment can significantly decrease the cyclic deformation resistance of the extruded 6061 alloy; under the higher applied total strain amplitude, the fatigue life of soiled solution state 6061 aluminum alloy was the longest while the fatigue life of the aging state 6061 aluminum alloy was the shortest; when applied total strain amplitude was low, the fatigue life of extruded 6061 aluminum alloy was higher than heat-treated alloy’s; to different heat treatment of extruded 6061 aluminum alloy, the relation between plastic and elastic strain amplitudes as well as reversals to failure can be described by Coffin-Manson and Basquin equations respectively.Fatigue fracture morphology analysis showed that the fatigue crack of different deformated 6061 aluminum alloy which were under the applied total strain-controlled fatigue loading conditions were transgranular mode to initiate in the fatigue specimen surface, and to extended in the transgranular mode.更多还原