论文部分内容阅读
本文利用连续切片技术研究了定向凝固Al-40%Cu过共晶合金中金属间化合物Al_2 Cu初生相的三维微观组织,以及抽拉速率跃迁下,三维共晶组织形态的演变和间距调整.结果表明:抽拉速率为5μm/s时,初生Al_2Cu三维组织沿生长方向存在棱面和棱角,表现出明显的棱面相生长形态;凝固过程中初生Al_2Cu相释放的结晶潜热使得生长界面发生局部重熔,三维组织中出现孔洞,形成拓扑缺陷.在Al-40%Cu合金三维共晶组织中,Al_2Cu相和Al相的体积分数分别为56.8%和43.2%,且Al_2Cu相的生长方向与试样轴向夹角为5.1°.当抽拉速率从2μm/s突然跃迁到500μm/s时,三维共晶组织形态从层片向棒状转变,这种转变不是由合金中两相体积分数变化造成的.三维共晶组织间距调整机制不同于二维组织中的分叉、内凹和界面重新形核,而是通过三维空间非同一平面连续的分叉、分枝进行,在三维下并没有观察到二维下的重新形核共晶间距调整机制.
In this paper, the three-dimensional microstructure of Al 2 Cu intermetallic compound in the directionally solidified Al-40% Cu hypereutectic alloy and the evolution and spacing of the three-dimensional eutectic microstructure were investigated by means of continuous slicing technique. The results show that the three-dimensional microstructure of primary Al 2 Cu has the facets and edges along the growth direction at a withdrawal rate of 5 μm / s, showing obvious growth of facets. The latent heat of crystallization released by the primary Al 2 Cu phase during solidification leads to local remelting , The holes appear in the three-dimensional structure, forming the topological defects.In Al-40% Cu alloy three-dimensional eutectic structure, the volume fractions of Al 2 Cu phase and Al phase are 56.8% and 43.2%, respectively, and the growth direction of Al 2 Cu phase and the sample axis And the included angle is 5.1 °. The three-dimensional eutectic microstructure changes from ply to rod when the pull-out rate suddenly changes from 2μm / s to 500μm / s, which is not caused by the change of the volume fraction of two phases in the alloy. Unlike the bifurcation, concavity and interfacial re-nucleation in two-dimensional structures, the mechanism of three-dimensional eutectic interplanar spacing is bifurcated and branched by non-uniform planes in three-dimensional space and not observed in three dimensions Re eutectic nucleation spacing adjustment mechanism in dimension.