中文摘要：

采用以5kWCO2激光器为光源的激光立体成形（LSF）系统制备了两种成分的Ti2AlNb基合金，借助金相显微镜（OM）、扫描电子显微镜（SEM）、能谱分析（EDS）、X射线衍射（XRD）方法及显微硬度测试，对合金的组织形貌、相组成以及硬度进行了分析。结果表明，原子数分数为Ti-20％Al-27％Nb（以下简称A1）时，沉积态合金的显微组织和相组成沿沉积方向呈现出B2（固溶体）→B2＋O（魏氏组织）→B2（固溶体）的变化特征；原子数分数为Ti-22％Al-27％Nb（以下简称A2）时，沉积态合金由枝晶β（TiNb）和枝晶间的B2＋O两相组成。在沿沉积高度增加方向上枝晶一次臂长度变化比较明显，从试样底部的25μm左右变化到试样顶部的80μm左右。A1合金的显微硬度从试样底部至顶部呈现低→高→低的变化趋势；A2合金整体的显微硬度变化不大。

英文摘要：

Ti2AlNb-based alloys of two different compositions were deposited using a 5 kW C02 laser. Optical microscope （OM）, scanning electron microscope （SEM）, energy-dispersive spectrometer （EDS）, X-ray diffraction （XRD） and microhardness testing method, were used to investigate the typical microstructure evolution, phase transformation and the corresponding hardness evolution. Experimental results show that for Ti-20% Al-27% Nb （atomic fraction） （A1）, the phase transformation occurrs. B2→B2 ＋ O→B2 along the laser deposition direction. While Ti-22 % Al-27 % Nb （A2） is mainly composed of β（TiNb） dendritic and B2 ＋ O in the interdendritic. The primary dendrite trunk spacing changes from 25 μm to 80 μm along the deposition direction. For the two different compositions Ti2AlNb-based alloys, the microhardness variation of A1 alloy along the deposition direction is low→high →low, which agrees well with the corresponding microstructure and phase transformation. The microhardness of A2 alloy distributes uniformly except the local region of the dendritic.