时效态Al-Zn-Mg-Cu-Zr-Sc合金的组织与疲劳性能

为了研究时效处理对Al-7.2Zn-2.5Mg-1.5Cu-0.08Zr-0.12Sc合金的组织与疲劳性能的影响,利用透射电子显微镜对合金的显微组织进行了观察分析,并针对不同时效状态的合金进行了低周疲劳实验.结果表明,经过150℃×6 h时效处理后,合金晶内析出相较少,晶界无析出相;经过150℃×36 h时效处理后,合金晶内析出相较为细小,并呈弥散分布,同时晶界析出断续分布的平衡相,并存在晶界无析出带;经过150℃×48 h时效处理后,合金的析出相均已长大,且晶界无析出带发生宽化.经过150℃×36 h时效处理后的合金,表现出了较高的循环变形抗力与较长的低周疲劳寿命;不同时效状态合金的塑性应变幅、弹性应变幅与载荷反向周次之间,以及循环应力幅与塑性应变幅之间均呈线性关系.

Microstructures and fatigue properties of aged Al-Zn-Mg-Cu-Zr-Sc alloy

In order to clarify the effect of aging treatment on both microstructures and fatigue properties of Al-7.2Zn-2.5Mg-1.5Cu-0.08Zr-0.12Sc alloy, the microstructural observation was performed with transmission electron microscope(TEM), and the low-cycle fatigue experiments were conducted for the alloys with different aging treatment states. The results show that after 150 ℃×6 h aging treatment, the precipitates inside the grains of the alloy are less, and there is no precipitates at the grain boundaries. After 150 ℃×36 h aging treatment, the precipitates inside the grains of the alloy are fine and dispersive. Meanwhile, the discontinuous equilibrium phase precipitates at the grain boundaries, and the precipitate free zones exist near the grain boundaries. After 150 ℃×48 h aging treatment, the precipitates in the alloy have already grown up, and the precipitate free zones near the grain boundaries widen. In addition, the alloy subjected to 150 ℃×36 h aging treatment has higher cyclic deformation resistance and longer low-cycle fatigue lives. The relationship between the plastic strain amplitude, elastic strain amplitude and reversals to failure as well as the relationship between the cyclic stress amplitude and plastic strain amplitude of the alloy with different aging treatment states are linear.