【作者】 安江；

【导师】 陈立佳；

【作者基本信息】 沈阳工业大学 ， 材料学， 2012， 硕士

【摘要】 因具有导电性能好、比强度高等优良的综合性能,铝合金已经广泛应用于桥梁建筑、电工电子等工业领域。Al-Mg-Si系铝合金具有良好的热塑性和优良的耐蚀性,近年来已经备受关注。为了改善Al-Mg-Si系铝合金的综合性能,常常在该系合金中添加适量的稀土元素。本文研究了挤压变形Al-0.8%Mg-0.6%Si与Al-0.8%Mg-0.6%Si -0.5%Er的室温低周疲劳行为,明确了稀土元素Er以及固溶+时效(T6)处理对挤压变形Al-0.8%Mg-0.6%Si系合金低周疲劳行为的影响。结果表明,稀土元素Er的添加可以细化挤压态和固溶+时效态Al-0.8%Mg-0.6%Si合金的晶粒尺寸。挤压变形Al-0.8%Mg-0.6%Si合金呈现出循环应变硬化、软化和循环稳定;挤压变形Al-0.8%Mg-0.6%Si-0.5%Er合金则表现为循环应变硬化与循环稳定。稀土元素Er的添加可以显著提高挤压态Al-0.8%Mg-0.6%Si合金的循环变形抗力;固溶+时效处理可以显著提高挤压变形Al-0.8%Mg-0.6%Si与Al-0.8%Mg-0.6%Si- 0.5%Er合金的循环变形抗力。对于挤压态和固溶+时效态Al-0.8%Mg-0.6%Si与Al-0.8%Mg-0.6%Si-0.5%Er合金而言,其载荷反向周次与塑性应变幅之间的关系服从Coffin-Manson公式,与弹性应变幅之间的关系则符合Basquin公式。稀土元素Er的添加会降低挤压态Al-0.8%Mg-0.6%Si合金的低周疲劳寿命,但可以提高固溶+时效态Al-0.8%Mg-0.6%Si合金在较高应变幅下的低周疲劳寿命。固溶+时效处理有利于提高挤压变形Al-0.8%Mg-0.6%Si合金在较低外加总应变幅下的疲劳寿命,而可以提高挤压变形Al-0.8%Mg-0.6%Si-0.5%Er合金在各个外加总应变幅下的低周疲劳寿命。不同处理状态的挤压变形Al-0.8%Mg-0.6%Si与Al-0.8%Mg -0.6%Si-0.5%Er合金的循环应力幅与塑性应变幅之间符合指数定律。挤压态和固溶+时效态的挤压变形Al-0.8%Mg-0.6%Si与Al-0.8%Mg-0.6%Si-0.5%Er合金的疲劳裂纹均萌生于疲劳试样表面并以穿晶方式扩展。更多还原

【Abstract】 Due to such excellent comprehensive properties as good electric conductivity and high specific strength, aluminum alloys have been widely applied in industrial fields such as bridge architecture, electric engineering and electronic engineering. The Al-Mg-Si series aluminum alloys exhibit good thermoplasticity and excellent corrosion resistance, and have received much attention in recent years. In order to improve their comprehensive properties, the rare earth elements with appropriate content are often added into the Al-Mg-Si series aluminum alloys. In this investigation, the low-cycle fatigue behavior of the extruded Al-0.8%Mg-0.6%Si and Al-0.8%Mg-0.6%Si-0.5%Er alloys at room temperature was studied, and the influence of rare earth element Er and solid solution plus aging (T6) treatment on the low-cycle fatigue behavior of the Al-0.8%Mg-0.6%Si series aluminum alloys was determined.The results show that the addition of rare earth element Er can refine the grains of the Al-0.8%Mg-0.6%Si alloys with both as-extruded and solid solution plus aging states. The extruded Al-0.8%Mg-0.6%Si shows the cyclic strain hardening, softening and stability. However, the extruded Al-0.8%Mg-0.6%Si-0.5%Er exhibits the cyclic strain hardening and stability. The addition of rare earth element Er can enhance the cyclic deformation resistance of as-extruded Al-0.8%Mg-0.6%Si alloy obviously. The solid solution plus aging treatment can increase the cyclic deformation resistance of the extruded Al-0.8%Mg- 0.6%Si and Al-0.8%Mg-0.6%Si-0.5%Er alloys. For the extruded Al-0.8%Mg-0.6%Si and Al-0.8%Mg-0.6%Si-0.5%Er alloys with both as-extruded and solid solution plus aging states, the relationship between reversals to failure with plastic strain amplitude can be well described by the Coffin-Manson equation, while the relationship between reversals to failure with elastic strain amplitude obeys the Basquin equation. The addition of rare earth element Er will decrease the low-cycle fatigue lives of as-extruded Al-0.8%Mg-0.6%Si alloy, but can prolong the low-cycle fatigue lives of the solid solution plus aging treated Al-0.8%Mg-0.6%Si alloy at higher imposed total strain amplitudes. The solid solution plus aging treatment is beneficial for improving the low-cycle fatigue lives of the extruded Al-0.8%Mg-0.6%Si alloy at lower imposed total strain amplitudes, and can also enhance the low-cycle fatigue lives of the extruded Al-0.8%Mg-0.6%Si-0.5%Er alloy at each imposed total strain amplitude. The relationship between the cyclic stress amplitude and plastic strain amplitude can be described by a power law. For the Al-0.8%Mg-0.6%Si and Al-0.8%Mg-0.6%Si-0.5%Er alloys with both as-extruded and solid solution plus aging states, the fatigue cracks initiate on the surfaces of fatigue specimens, and propagate transgranularly.更多还原