Tan Hua, Mi Zesen, Zhu Yongshuai, Yan Zhenyu, Hou Xin, Chen Jing
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China.
Capital Aerospace Machinery Co., Ltd., Beijing 100076, China.
Materials (Basel). 2020 Jan 23;13(3):552. doi: 10.3390/ma13030552.
TA15/TiAlNb multiple-layer samples and a dual-alloy sample were fabricated by laser solid forming (LSF) in this study. The formation mechanism of the dilute region and microstructure evolution of the dual alloy were analyzed. The results confirmed a "step" distribution of the composition among several initial layers in the multiple-layer samples, which can be explained by calculating the ratio of the remelted zone to the deposited TiAlNb zone in each deposited layer. However, the "step" compositional distribution disappears, and the compositional variation tends to be more continuous and smooth in the TA15/TiAlNb dual-alloy sample, which is attributed to alloy elements' diffusion at the subsequent multiple re-melting and the longer thermal cycle. The macrostructure of the TA15/TiAlNb dual-alloy sample consists of epitaxially grown columnar prior β grains at the TA15 side and equiaxed grains at the TiAlNb side, while the microstructure shows a transition of α+β→α+α+β/B2→α+β/B2→α+B2+O with increasing amounts of TiAlNb, leading to the microhardness also changing significantly.
本研究采用激光立体成形（LSF）制备了TA15/TiAlNb多层试样和双合金试样。分析了双合金中稀释区的形成机制及微观组织演变。结果证实了多层试样中几个初始层间成分呈“阶梯”分布，这可通过计算各沉积层中重熔区与沉积TiAlNb区的比例来解释。然而，在TA15/TiAlNb双合金试样中，“阶梯”成分分布消失，成分变化趋于更连续和平滑，这归因于合金元素在随后多次重熔时的扩散以及更长的热循环。TA15/TiAlNb双合金试样的宏观组织由TA15侧外延生长的柱状初生β晶粒和TiAlNb侧的等轴晶粒组成，而微观组织随TiAlNb含量增加呈现α+β→α+α+β/B2→α+β/B2→α+B2+O的转变，导致显微硬度也发生显著变化。
