目的 探索喷射沉积7075铝合金在半固态触变成形过程中的微观组织演变规律及工艺参数对成形性能的影响,为优化触变成形工艺提供理论支持和实践指导。方法 选取直径900 mm、高度600 mm的喷射沉积7075铝锭为研究对象,通过热模拟试验平台设计等轴压缩模具,开展不同温度（510、540、570、600 ℃）、不同保温时间（60、120、300 s）及不同压下量条件下的半固态触变成形试验。在试样触变成形结束后快速水冷并分割,利用光学显微镜分析微观组织特征。同时,结合有限元模拟对不同区域的等效应变量进行计算,研究应变分布与微观组织之间的关联。结果 随成形温度与保温时间的增加,喷射沉积7075铝合金的晶粒逐渐粗大并趋于球形化,晶界区域液相体积增加并形成网络状结构。在较高温度（570 ℃）条件下,液相从中心区域向边缘流动,引发液相偏析现象。此外,孔隙数量减少但孔隙体积有所增大。结论 喷射沉积7075铝合金在半固态触变成形过程中表现出显著的微观组织演变特征,成形温度对液相分布及晶粒球化的影响显著。570 ℃和60 s的成形参数能够有效平衡晶粒球化与共晶物溶解过程,提升成形性能。为解决裂纹与孔隙问题,建议采用闭式模具设计以促进液相填充并抑制液相外流导致的偏析现象。
Abstract
The work aims to explore the microstructural evolution of spray-formed 7075 aluminum alloy during semi-solid thixoforming and investigate the effects of process parameters on the forming performance, providing theoretical support and practical guidance for optimizing thixoforming processes. A spray-formed 7075 aluminum alloy ingot with a diameter of 900 mm and a height of 600 mm was selected for the study. An isothermal compression mold was designed through a thermal simulation test platform to conduct semi-solid thixoforming experiments under different temperatures (510, 540, 570, and 600 ℃), holding time (60, 120, and 300 s), and compression amounts. After thixoforming, the specimens were rapidly water-cooled, sectioned, and analyzed with an optical microscope to examine microstructural characteristics. Finite element simulations were also conducted to calculate equivalent strain distributions and analyze their correlations with the microstructure. As the forming temperature and holding time increased, the grains of the spray-formed 7075 aluminum alloy became coarser and more spherical, while the liquid phase at grain boundaries increased and formed a network structure. At higher temperatures (570 ℃), the liquid phase migrated from the central region to the edges, resulting in liquid phase segregation. Additionally, the number of pores decreased, but the pore volume increased. Spray-formed 7075 aluminum alloy exhibits significant microstructural evolution during semi-solid thixoforming, with forming temperature having a pronounced impact on liquid phase distribution and grain spheroidization. The forming parameters of 570 ℃ and 60 s effectively balance grain spheroidization and eutectic dissolution, enhancing the forming performance. To mitigate cracking and porosity issues, it is recommended to use closed molds to promote liquid phase filling and suppress segregation caused by liquid phase migration.
关键词
喷射沉积 /
7075铝合金 /
半固态成形 /
触变成形 /
微观组织演变
Key words
spray forming /
7075 aluminum alloy /
semi-solid forming /
thixoforging /
microstructural evolution
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基金
科技部重点研发计划（2022YFB3403701）
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