铝合金固溶体脱溶行为的动态电阻响应解析及关联机理研究

An in-situ electrical resistivity measurement setup has been developed by the laboratory to collect dynamical resistivity signals during the continuous cooling processes of the 7xxx Al alloy. Based on the obtained response curves of dynamic resistance, the response characteristics of precipitation behavior for different cooling conditions and phases will be studied. And then, the study will be investigated by means of testing tools and numerical methods such as High resolution transmission electron microscopy (HRTEM), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Artificial neural network (ANN). Moreover, a series of solid electronic theories and solid state phase transformation theories will be involved. The internal cause of electrical resistance evolution of the alloy during different condition will be analyzed. And the physical interpretation for each stages of the curve will be discussed. Finally, this research will reveal the dynamical resistivity singals generated by multi-size microstructures evolution and an electrical resistance response model will be developed to describe the precipitation behavior of the supersaturated solid solution. The result of this investigation will offer theory supports to the in-situ control of precipitation sequences, particle size and density during the quenching process.

采用自主开发的动态电阻捕捉系统对7系铝合金淬火冷却过程的电阻响应信息进行原位捕捉，获得不同冷却阶段脱溶行为的动态电阻响应规律。综合利用高分辨透射电子显微镜、透射电子显微镜、扫描电镜、差式量热分析仪、X射线衍射分析仪以及人工神经网络等实验分析方法和数值分析方法，根据固体电子理论和固态相变理论，深入研究典型冷却条件下合金电阻率的变化的内在原因，分析曲线不同阶段对应的物理意义，探明多尺度微结构演变激发的特征动态电阻信号，建立描述铝合金固溶体连续冷却过程脱溶行为的电阻响应模型，为在线灵活控制析出相的类型、数量、大小及其分布提供理论基础。

固溶体脱溶行为的研究是调控铝合金组织性能的基础，本项目以动态电阻技术为基础深入研究铝合金非线性连续冷却过程的脱溶行为，具有重要的科学和工程实践意义。本项目主要完成了如下工作：一是在基金的资助下，优化了自主开发的动态电阻测试系统，提高了测试系统的稳定性和灵敏性；二是采用牛顿方程模拟了样品的非线性冷却过程，获得了冷却曲线的数值表征方程，探明了动态电阻曲线随温度和冷却速度的变化规律。三是确定了冷却前原始组织及冷却过程中的温度变化激发的电阻响应信息，引入了相对电阻率曲线解析铝合金的非连续冷却脱溶转变，确定了脱溶序列，构建了非线性冷却脱溶转变模型和冷却脱溶行为的电阻响应模型；四是对项目获得的研究成果进行了初步的应用研究，根据动态电阻曲线的变化，确定铝合金在不同冷却条件下的相变温度点，绘制出相应的连续冷却转变图（CCT图），研究了非线性冷却过程中的脱溶行为对铝合金时效组织性能的影响。