Al-Cu-Mg-Ag新型耐热铝合金循环蠕变中的动态析出行为与微观损伤机制

Due to the great potential damage risk of metal materials during the cyclic creep process, their microscopic damage mechanisms have great scientific signification and engineering value for life prediction and safety assessment of engineering components. Based on dynamic precipitation mechanism of the strengthening phase, this project would investigate the dynamic precipitation behavior of the strengthening phase under cyclic loading and the microscopic damage mechanism during cyclic creep for a new kind of under-aged Al-Cu-Mg-Ag aeronautic heat-resistant aluminium alloy. The main research contents include: (1) Study the influence of cyclic loading on the dynamic precipitation behavior of the strengthening phase and define the effect of dynamic precipitation on cyclic creep properties of the alloy. (2) Reveal the creep fatigue interaction mechanism under different cyclic creep conditions and illuminate the cyclic creep microscopic damage mechanism of Al-Cu-Mg-Ag alloy. (3) Establish a prediction model of the cyclic creep life of Al-Cu-Mg-Ag alloy according to the continuum damage mechanics theory. Smooth implementation of this project will provide significant scientific basis for further revealing the cyclic creep damage mechanism and life prediction of this kind of aluminium alloy.

金属材料循环蠕变损伤潜在危险性极大，其微观损伤机制对工程构件的寿命预测和安全评估具有重要的科学意义与工程价值。基于强化相的动态析出原理，本项目以欠时效态Al-Cu-Mg-Ag新型航空耐热铝合金为对象，解析循环载荷下强化相的动态析出行为，探讨合金循环蠕变微观损伤机制。主要研究内容包括：（1）研究循环载荷对强化相动态析出行为的影响规律，明确强化相的动态析出对合金循环蠕变性能的影响机理；（2）揭示不同循环蠕变条件下合金的蠕变-疲劳交互作用机理，阐明Al-Cu-Mg-Ag合金的循环蠕变微观损伤机制；（3）基于连续介质损伤力学理论，构建Al-Cu-Mg-Ag合金的循环蠕变寿命预测模型。通过本项目的开展将为进一步揭示该类铝合金的循环蠕变损伤机理及其寿命预测提供重要的科学依据。

本项目以欠时效态Al-Cu-Mg-Ag新型航空耐热铝合金为对象，解析循环载荷下强化相的动态析出行为，探讨合金循环蠕变微观损伤机制。主要研究成果如下：（1）对比研究了欠时效和峰时效态Al–Cu–Mg–Ag合金在恒定载荷和循环载荷下的蠕变行为。发现经过欠时效处理后A1-Cu-Mg-Ag合金无论是在恒定载荷下还是在循环载荷下，其蠕变速率均低于峰时效态处理试样；与峰时效态合金相比，恒定载荷下，欠时效态合金的蠕变速率降低了9.35%，循环载荷下，欠时效态合金的蠕变速率降低16.88%；欠时效态合金蠕变后强化相的尺寸小于峰时效态试样，长大速率较低，导致欠时效态合金在两种载荷下的抗蠕变性能均高于峰时效态合金。（2）研究了循环载荷作用下Al–Cu–Mg–Ag合金蠕变的宏观特征，发现欠时效态A1-Cu-Mg-Ag合金无论是在低应力还是在高应力条件下，其在循环载荷下的蠕变速率均低于恒定载荷；外加载荷越大，与纯蠕变试样相比，循环蠕变试样中Ω相和θ′相越多，尺寸越小，其抗蠕变性能提高幅度越大。欠时效处理后的合金在进行循环蠕变试验时，随着温度的升高，合金晶内强化Ω相和θ′相尺寸均变大，抗蠕变性能降低；随着外加应力的增大，尽管合金中Ω相和θ′相尺寸均减小，但θ′相数量增多，其强化效果减小，抗蠕变性能降低。（3）确定了合金循环蠕变性能的主要影响因素，发现加载时间对本实验条件下合金的蠕变性能影响不大；欠时效态Al-Cu-Mg-Ag合金循环蠕变时，其稳态蠕变速率随着试验温度的升高和蠕变应力的增大均逐渐增大，构建了Al–Cu–Mg–Ag合金蠕变速率与蠕变条件之间的预测模型。为该合金循环蠕变过程中稳态蠕变速率的预测提供依据。