中文摘要：

针对高功率条件下激光立体成形Ti-6Al-4V合金组织特征展开研究,揭示高功率条件下组织形成机理,并对比分析了高功率与中/低功率条件下组织形成的差异及原因。结果表明：由于高功率条件下具有更低的温度梯度和更高的凝固速度,激光立体成形Ti-6Al-4V合金的宏观组织由粗大的柱状晶、竹节状的小柱状晶和等轴晶三部分组成,并且沉积层之间存在层带;而中/低功率条件下只有贯穿多个沉积层呈外延生长的粗大的柱状晶。高功率条件下层带内典型微观组织是由大量的魏氏α集束组成,而层带间为α板条编织成的网篮状组织,并且部分α相球化成等轴状。与中低功率条件下典型组织相比,高功率条件下α板条长宽比明显减小,不存在针状α。

英文摘要：

The microstructure characterization of laser solid forming （LSF） Ti-6Al-4V alloy by high power was investigated, the mechanism of the microstructure formation by high power LSF was revealed, and the differences and reasons of microstructure forming were analyzed compared with the low power LSF. The results indicate that because of lower temperature gradient and higher speed of solidification by high power, the macrostructure consists of three sections： bulky columnar crystal, small bamboo-like columnar crystal and equiaxed grains. The layer band exists in each deposited layer. But only the bulky columnar crystal through multiple layers grows epitaxially from the substrate along the deposition direction by low power LSF. The microstructure within layer band consists of colonies of Widmanstatten a lath outlined in retained fl, while the microstructure between the layer bands consists of basketweave Widmanstatten a lath, and some of them are spheroidized into equiaxed a lath. Compared with typical microstructure by low power, the length-width ratio of the a lath decreases obviously, and no needle a lath exists.