半固态Al-4Cu-Mg合金变形时的微观组织演化

【作者】 黄维超；

【导师】 李淼泉；

【作者基本信息】 西北工业大学 ， 材料加工工程， 2004， 硕士

【摘要】 合金在半固态变形时内部的微观组织会经历一系列动态变化，微观组织的变化又会影响材料的变形过程，最终影响变形后工件的性能。正确理解变形工艺对微观组织的影响，探讨变形过程的微观机理，并建立变形过程中的微观组织演化模型，可以为制定合理的变形工艺提供理论与实验依据，并为发展半固态成形技术奠定基础。 本文研究了应变诱发熔化激活法制备的半固态Al-4Cu-Mg合金的半固态压缩变形过程。采用热模拟压缩实验和定量金相技术分析了变形工艺参数(包括变形温度、变形程度和应变速率)对材料内部微观组织参数(晶粒等效直径和分形维数)的影响，对比了半固态变形与高温变形微观组织的异同以及供应态合金与半固态合金变形的异同。通过对变形后试样的TEM和SEM观察，初步研究了半固态变形机理，并研究了变形中产生的孔洞、液相宏观偏析、成分偏析等缺陷的形成规律。 最后，结合模糊数学和神经网络理论的优点，建立了Al-4Cu-Mg合金半固态变形过程中微观组织演化的模糊神经网络模型，并对该模型的可靠性进行了测试。测试结果表明：该模糊神经网络模型计算精度高，晶粒等效直径的计算误差在10％以内，分形维数的计算误差在15％以内。运用此模型计算了Al-4Cu-Mg合金半固态变形过程中的微观组织参数，计算结果与实验结果吻合。更多还原

【Abstract】 During the semi-solid forming, the microstructure in materials undergoes a series of dynamic changes, which will affect the deformation behavior of materials and servicing properties of workpieces. To understand the effects of process parameters on microstructure variables, and explore the deformation mechanism and establish the model for microstructural evolution in the semi-solid forming can provide the theoretical and technological foundation for optimizing the process parameters and developing the semi-solid technique.Effect of the process parameters, including deformation temperature, height reduction and strain rate, on microstructure variables, including the grain size and the fractal dimension, has been investigated by the isothermal compression and quantitative metallography examination. The distinctions of microstructure between the semi-solid forming and high temperature deformation of the Al-4Cu-Mg alloy as received and semi-solid Al-4Cu-Mg alloy has been investigated. Meanwhile, the semi-solid deformation mechanism has been investigated by TEM and SEM, and the defective structure, including cavity, liquid phase segregation and constituent segregation, has been investigated.In the end, integrating the advantages of the fuzzy set and the artificial neural network theory, a microstructural evolution model during the semi-solid forming has been established according to the experimental results. Meanwhile, the present model is checked. The comparison of the calculated results with the experimental of the test samples shows that the maximun error of grain size is less than 10%, and which of fractal dimension is less than 15%. The microstructural variables of Al-4Cu-Mg alloy has been calculated during semi-solid forming.更多还原