真空铜模吸铸TiAl基合金凝固行为

Solidification Behavior of TiAl-Based Alloy Prepared by Cu-Mold Vacuum Suction Casting

采用真空铜模吸铸技术成功制备了Ti-45Al-2Cr-2Nb合金铸件。借助扫描电镜(SEM)、能谱(EDS)及X射线衍射仪(XRD)分析铸态和吸铸条件下显微组织形貌特征、各相成分以及相组成,并且和铸态组织进行了比较研究。结果表明:铸态和吸铸凝固组织的主要相组成均为α_2相和γ相。铸态显微组织观察与Al当量计算结果一致,铸态Ti-45Al-2Cr-2Nb合金是以β为初生相的单一β相凝固合金;吸铸糊状区凝固组织明显细化,晶粒尺寸由244μm细化至96μm,同时降低了凝固偏析,呈现胞状枝晶形貌,枝晶干上存在白色脉络状的β型偏析和残余的条状α相,在表面急冷区观察到块状γ相(γ_m)和羽毛组织(γ_f),块状γm相区域的厚度约为62μm。

The Ti-45Al-2Cr-2 Nballoy sample was achieved by Cu-mold vacuum suction casting. The microstructure in different area, component distribution and phase constitution were studied by means of scanning electron microscopy(SEM), energy dispersive spectroscope(EDS) and X-ray diffraction(XRD), respectively, and compared with as-cast one. The results indicate that the microstructures of as-cast and suction-casting alloysboth mainly consist of α2 and γ phase. The as-cast microstructure observation is consistent with the calculation result of Al-equivalent. The primary phase is β phase and the solidification structure is the singleβ-phase. Compared with the as-cast microstructure, the microstructure of vacuum suction casting alloy is apparently refined from 244 μm to 96 μm. At the same time, the solidification segregation was reduced and the morphology of dendrite cell was presented. White veins β-segregation and residual striped α-phase were shown inside dendrites.γm and γf were observed in surface quenching zone. Thickness of region of γm phase was about 62 μm.