8090Al—Li合金焊缝金属形核机制

NUCLEATION MECHANISM OF 8090 Al-Li ALLOY WELD METAL

８０９０Ａｌ—Ｌｉ合金焊缝凝固组织中除了柱状枝晶和等轴枝晶外，还有一种极细小的等轴非枝晶，它主要分布在熔合区边缘，有时也能呈带状出现在焊缝中部．等轴枝晶与柱状枝晶的结晶核心是平衡态四方Ａｌ_３Ｚｒ粒子，而等轴非枝晶的结晶核心是亚稳态立方Ａｌ_３Ｚｒ粒子．

A kind of very fine equiaxed non- dendrite, besides the equiaxed dendrites and the columnar dendrites, exists in the 8090 aluminum-lithium alloy welds. The equiaxed non-dendrites are mainly distributed at the edge of the fusion zone; occasionally they can appear in the intermediate section of weld in the form of banding. The nuclei of equiaxed dendrites and columnar dendrites are the equilibrium tetragonal Al_3Zr particles, while the nuclei of equiaxed non -dendrite are demonstrated to be metastable cubic Al_3Zr particles.