磁场辅助激光沉积修复钛合金的组织和性能

Microstructure and Properties of Magnetic Field Assisted Laser Deposition Repaired BT20 Alloy

摘要:

为了调控激光沉积修复BT20钛合金的组织，提高其力学性能，将旋转磁场引入到激光修复系统中，考察了不同磁场强度下修复试样的组织和力学性能。结果显示，修复区和基体形成了致密冶金结合，修复区为α/β片层组织，硬度分布从基材到修复区依次提高；在一定范围内，磁场强度越强，α片层长/径比越小，片层组织越细密，修复区硬度越大，HV0.1可达4.4 GPa。表明磁场搅拌减轻了β晶溶质富集，使α片层析出的驱动力减小，需要在更大过冷度下析出，而过冷度的增加，导致形核率的增大，最终导致α层片细化，从而提高沉积层的力学性能。

Abstract:

To improve the laser deposition repair quality of BT20 titanium alloy, a magnetic field device was designed and introduced to the laser repair system. The effects of magnetic field intensity on the macro morphologies, microstructures and micro-hardness of the laser repaired zone were studied. The results show that there is a dense metallurgical bond between the repaired zone and the substrate under the magnetic field, and flat surface can be gained with few powders. And also, the repaired zone is composed of prior β grain with α/β lamellae in it. With the increasing of magnetic field, the α lamellae length declines and its thickness is 0.4~0.5 μm. The micro-hardness of the repaired zone improves with the increasing of magnetic field intensity, but it tends to be homogenization in certain parameters. It indicates that rotating magnetic field reduces enrichment of solute, and then decreases β→α phase transformation driving force. Hence, α lamellae precipitation needs high degree of supercooling, which lead to a higher nucleation rate, resulting in finer microstructures and improved mechanical property.