Research on High Strength and High Toughness TC11 Titanium Alloy with Multi Laser Coaxial Wire Feeding and Directed Energy Deposition

Researchers from Huazhong University of Science and Technology, AVIC Xi'an Aircraft Design and Research Institute, AVIC Xi'an Aircraft Industry Group Co., Ltd., Shanghai Aerospace Equipment Manufacturing General Factory Co., Ltd., State Key Laboratory of Aircraft Control Integration Technology, Beijing Xinghang Electromechanical Equipment Co., Ltd. and Nanjing Yingigma Automation Co., Ltd. reported on the research progress of high-strength and high toughness TC11 titanium alloy deposited by multi laser beam coaxial wire feeding directional energy, and the related research was published in Next under the title of "Multi laser beams directed energy disposition of a high strength and high strength TC11 titanium alloy with coaxial wire feeding". Materials.

Article focus:
Developed a new type of multi laser beam coaxial wire feeding processing head
Optimizing process parameters to achieve good formability of TC11 alloy
Revealed the mechanism of thermal gradient and heterogeneous nucleation

The wire feeding laser directed energy deposition (WLDED) additive manufacturing technology uses metal wire as raw material, which has the advantages of high material utilization and low pollution, and is suitable for efficient processing of large components. However, the traditional side axis wire feeding method has problems such as insufficient laser wire coupling and limited flexibility of the processing head, making it difficult to meet the manufacturing needs of complex parts. This study designed a multi laser beam coaxial wire feeding device for the preparation and analysis of high-strength and high toughness TC11 titanium alloy, a commonly used material for key load-bearing components in aviation. By optimizing parameters such as wire feeding speed (500 mm/min) and scanning speed (4 mm/s), the formability has been significantly improved. Research has shown that the unique thermal gradient (G) and solidification rate (R) characteristics of coaxial WLDED, as well as the laser wire coupling position, can significantly affect the microstructure evolution and typical directional mechanical properties in different regions; The synergistic effect of lower thermal gradient and heterogeneous nucleation brought by coaxial ribbon feeding plays a decisive role in refining the microstructure of materials. This elucidates the microstructural evolution mechanism and tensile performance improvement mechanism of multi laser beam WLDED process for coaxial machining heads.

Keywords: additive manufacturing; Microstructure; Mechanical properties; Laser directed energy deposition; tc11 alloy

Figure 1. Coaxial WLDED method: (a) Design of six laser beam coaxial processing head; (b) Schematic diagram of sedimentation process; (c) Physical processing head

Figure 2. Single channel deposition morphology with wire feeding speed of 200-400 mm/min and scanning speed of 1-4 mm/s

Figure 3. Study on the Characteristics of Single Channel Sedimentary Sections: (a) Definition of Geometric Features; (b) Surface morphology under different parameters; (c) Sectional morphology under different parameters

Figure 4. Distribution of geometric features of the melt path under different parameters (the red area is the key influencing factor): (a) width/height/melt depth; (b) Dilution rate; (c) Aspect ratio; (d) Contact angle

Figure 5. Multi layer sedimentation cross-section (parameters: (a) wire feeding 400 mm/min scanning 3 mm/s, (b) 500 mm/min scanning 4 mm/s, (c) 600 mm/min scanning 5 mm/s); (d) Effective sedimentary area; (e-g) Microhardness distribution of the corresponding sample (yellow for sedimentary layer, gray for matrix)

Figure 6. Block specimen: (a) Macroscopic morphology; (b) Grain size evolution

Figure 7. Sedimentary TC11 block: (a) IPF diagram; (b) Tensile performance and fracture morphology; (c-d) Polar diagram

This study used a novel coaxial WLDED process to prepare a widely used high-strength and high toughness TC11 titanium alloy. Through systematic research on deposition formability, microstructure, and mechanical properties, grain size control and promotion of columnar equiaxed crystal transformation (CET) were successfully achieved. The main conclusions are as follows:

(1) We have developed a multi laser beam coaxial wire feeding processing head, which can achieve uniform heating of wire and molten pool. By analyzing the effects of scanning speed, wire feeding speed, and peak power on forming characteristics such as dilution ratio, aspect ratio, and contact angle, a fitting calculation formula was established to determine the optimized process parameter window.

(2) Further optimize multi-layer printing parameters based on hardness changes and prepare bulk samples. The microstructure and grain size evolution in different regions are highly correlated with the WLDED process, which is determined by the R/G values unique to coaxial processes and the laser wire coupling position. Its typical mechanical properties are superior to traditional additive manufacturing technology.

(3) The current research focuses on single channel/multi-layer/block deposition under limited conditions. Subsequent studies should investigate the effects of heat treatment regimes and multi phase transformations on tissue properties to further enhance the engineering applicability of WLDED technology.

Source: Yangtze River Delta Laser Alliance