超声对直接激光沉积钛基复材中未熔TiC聚集现象的影响

目的 改善直接激光沉积TiCp增强TC4复合材料中未熔TiC(Unmelted TiC，UMT)的聚集情况，提高钛基复合材料的力学性能。方法 利用定点超声辅助直接激光沉积工艺制备了20%、30%(质量分数)TiCp/TC4复合材料，通过金相显微镜观察UMT的分布情况，采用X射线衍射仪分析物相组成、衍射峰强度与半峰宽变化。通过扫描电子显微镜(SEM)进一步分析样件的微观组织，并使用SEM配备的能谱仪模块对元素分布情况和元素含量进行分析，同时观察拉伸样件的断口微观形貌和初生TiC情况。分别采用显微硬度仪和微机控制电子万能试验机测试样件的显微硬度与拉伸性能。结果 超声产生的声流、空化和机械效应不断搅拌熔池，增大了熔池的润湿性，初生TiC熔化/溶解更加充分，改善了UMT在熔覆层边缘的聚集情况。在超声能场辅助作用下，20%、30%(质量分数)TiCp/TC4复合材料的平均显微硬度分别提升了8.4%和12.7%，极限拉伸性能分别提升了8.0%和15.0%。结论 定点超声高频振动可以有效改善UMT聚集现象，使TiCp在TC4基体中分布得更加均匀，增强了熔覆层间结合强度，最终使沉积件力学性能得到提升。

Effect of Ultrasound on Aggregation of Unmelted TiC in Titanium Matrix Composite by Direct Laser Deposition

The work aims to improve the aggregation of UMT in TiCp reinforced TC4 composite fabricated by direct laser deposition to strengthen the mechanical properties of TMC. 20wt.% and 30wt.% TiCp/TC4 composites were prepared by fixed ultrasonic assisted direct laser deposition. The distribution of UMT was observed by metallographic microscope. The phase composition, diffraction peak intensity and half peak width were analyzed by X-ray diffractometer. The microstructure was analyzed by field emission scanning electron microscope. The element distribution and element content were analyzed by energy dispersive spectrometer of SEM. At the same time, the fracture morphology and primary TiC of tensile samples were observed. The mechanical properties of the samples were tested by microhardness tester and microcomputer controlled electronic universal testing machine. The acoustic flow, cavitation and mechanical effects generated by ultrasound could continuously stir the molten pool, increase the wettability of the molten pool, make the primary TiC melt/dissolve more fully, and improve the aggregation of UMT at the edge of the cladding layer. Under the assistance of ultrasonic energy field, the average microhardness of 20wt.% and 30wt.% TiCp/TC4 composites increased by 8.4% and 12.7% respectively, and the ultimate tensile properties increased by 8.0% and 15.0% respectively. The fixed ultrasonic high-frequency vibration effectively improves the UMT aggregation, makes the distribution of TiCp in the TC4 matrix more uniform, enhances the bonding strength between the cladding layers, and finally improves the mechanical properties of the deposited samples.