河南理工大学 2009 届本科毕业论文摘摘 要要本文利用真空电磁感应定向凝固装置分别研究了体积凝固状态下和定向凝固条件下FeCoNiCrAl高熵合金的组织特征和力学性能。研究结果表明: 体积凝固条件下FeCoNiCrAl高熵合金具有简单的BCC结构，FeCoNiCrAl高熵合金铸态组织为典型的树枝晶。 FeCoNiCrAl高熵合金在定向凝固过程中，随着抽拉速度的增大，凝固界面发生平-胞-枝转变，并且胞晶数目增多，胞晶间距减小，利用平界面凝固的稳定性判据进行了平胞界面转变的理论分析。对体积凝固和定向凝固试样分别进行了显微硬度测试。结果表明，体积凝固条件下枝晶间的显微硬度比一次枝晶干的硬度大，是因为铬原子容易在枝晶间发生偏析，而且铬原子的体积相对其他原子较大，造成晶格的畸变较大的缘故。定向凝固区域的硬度小于淬火区的硬度，是由于定向凝固缓慢的凝固过程造成了晶格畸变的减少，降低了硬度。关键词：FeCoNiCrAl 合金；定向凝固；界面形态；显微硬度河南理工大学 2009 届本科毕业论文I AbstractIn this paper, Microstructure and mechanical properties of FeCoNiCrAl high-entropy alloy were investigated under the bulk solidification and directional solidification respectively. The results show that the as-cast microstructure of FeCoNiCrAl high-entropy alloy have simple BCC structure. Typical dendritic structures are observed in the alloy. During the directional solidification, the planar-cellular-dendritic transition of solidification interface can be found with increasing growth velocity. Meanwhile, the number of cellular increases but cellular spacing decreases. Stability criterion of plannar to celluar interface is employed to analyse the interface morphology of directionaly solidified FeCoNiCrAl high-entropy alloy.Experimental investigation was carried out on the microhardness of FeCoNiCrAl alloy under the both bulk solidification and directional solidification condition. The interdendritic microhardness is larger than the one in the first dendritic, because Cr atoms are rich in the interdentrictic segregation, and atom radius of Cr is larger than that of other elements, distortion of crystal lattice is more severe, and microhardness in the directional solidification zone is smaller than the one in the as-quenched due to little distortion of crystal lattice during directional solidification. Keywords: FeCoNiCrAl alloy;directional solidification; interface morphology; microhardness河南理工大学 2009 届本科毕业论文II 目录目录摘要I Abstract II 第 1 章 绪论1 1.1 课题背景1 1.2 定向凝固技术发展与研究现状2 1.2.1 定向凝固技术的发展与应用2 1.2.2 定向凝固理论研究现状7 1.3 多主元高熵合金研究现状及发展前景9 1.3.1 多主元高熵合金研究现状9 1.3.2 多主元高熵合金的发展前景17 1.4 本论文研究的主要内容18 第 2 章 实验材料及实验方法19 2.1 研究方案19 2.2 实验设备19 2.3 实验方法21 2.3.1 实验合金及金相试样的制备21 2.3.2 温度采集系统22 2.3.3 定向凝固过程25 2.4 显微组织分析25 第 3 章 FeCoNiCrAl 合金定向凝固组织演化规律26 3.1 引言26 3.2 FeCoNiCrAl 合金体积凝固组织分析26 3.3 FeCoNiCrAl 合金定向凝固组织演化规律27 3.3.1 FeCoNiCrAl 合金定向凝固组织27 3.3.2 固/液界面形态30 3.3.3 胞晶间距31 3.4 理论分析32 3.5 显微硬度33 3.5.1 体积凝固组织的显微硬度33 3.5.2 定向凝固组织的显微硬度34 3.6 本章小结35 结论36 致谢37 参考文献