Guide
Since the advent of lasers, it has brought great changes to the manufacturing industry. Laser manufacturing technology offers many advantages, such as high quality, environmental friendliness, high selectivity, and the ability to perform a variety of processing operations, including additive manufacturing and welding. Therefore, lasers have been widely used in aerospace, automotive, and rail transit. In the development of laser manufacturing technology, near-infrared lasers have always been dominant. However, challenges arise when dealing with highly reflective metals such as copper and aluminum, as they can have a reflectivity of up to 95%. It is important to note that the absorption rate of copper and other highly reflective metals is greatly affected by different laser wavelengths. In this review, we review and analyze the literature and summarize the current status and challenges of using green and blue lasers to fabricate highly reflective metals. In addition, considering the limitations of a single laser, we summarize the current status of infrared-blue laser hybrids in manufacturing and provide guiding insights for the manufacture of highly reflective metals.
Main charts
Figure 1. Schematic diagram of the physical interactions of absorption, reflection, transmission, refraction, and scattering between a laser beam and a material.
Figure 2. Light absorption rate of Cu.
Figure 3. Schematic diagram of a green laser based on the ceramic Nd:YAG.
Figure 4. Experimental setup.
Figure 5. The schematic diagram illustrates the principles and processing characteristics of each technology, including advantages and limitations.
Figure 6.Application parts of pure copper.
Figure 7. Photomicrograph of a copper sample fabricated using a DOE optimization parameter set.
Figure 8. Geometry of a pure Cu lattice structure. (a) Computer-aided design of unit cell and lattice structures. (b) Optical photograph of a pure Cu lattice structure fabricated by L-PBF with a green laser beam.
Figure 9. Mechanical properties of pure Cu lattice structures. (a, b) Nominal compressive stress-strain curves for Oct and Cub structures at various strain rates. Comparison of (c) 2% offset yield stress, (d) 20% flow stress, and (e) absorbed energy for Oct and Cub structures under compression deformation.
Figure 10. Schematic diagram of BJ-AM process steps.
Figure 11. Frame for high-speed imaging of copper deposits on a copper matrix using 1 kW power, 1 g/min powder feed rate, and 0.1 m/min cladding speed. (a) The reference diagram represents the region of interest. (b) Progress of the process: As the laser beam moves forward, the melt pool shifts (white circles indicate areas of interest) and (c) powder particles merge into the melt pool (white circles mark the location of powder particles).
Figure 12. Frame for high-speed imaging of copper deposition on aluminum using 1 kW laser power, 0.5 m/min cladding speed, and 1.3 g/min powder feed rate. (a) A reference map representing the area of interest; (b) Frame sequence of powder particles incorporated into the melt pool and (c) frame sequence of powder particles reaching the oxide epidermis (white circles mark the location of powder particles).
Figure 13. Blue laser system: (a) Schematic diagram of the optical path, (b) Schematic diagram of the laser diode cluster, (c) Photographs of the blue laser equipment, (d) Photographs of the blue laser passing through water. LD: laser diode.
Figure 14. Blue laser and near-infrared laser welded surfaces.
Figure 15. Longitudinal section of CuSn6.
Figure 16. The welding depth of CuSn6 and Cu-ETP at a constant laser power of 147.7 W depends on the feed rate (the vertical scale is the same for CuSn6 and Cu-ETP).
Figure 17. CuSn6 connector structure (a) butt connector 0.15 mm; (b) Lap joint 0.15 mm; (c) Butt joint 0.3 mm.
Figure 18. (a) Robotic blue laser welding device (b) Laser welding head.
Figure 19. The appearance of the sample.
Figure 20. Development of blue diode laser systems.
Figure 21. Experimental setup for additive manufacturing using a blue diode laser.
Figure 22. X-ray observation of the laser coating using a blue laser. (a) Laser energy density: 1221 kJ/cm2 (b) Laser energy density: 732 kJ/cm2 (c) Laser energy density: 523 kJ/cm2 (d) Laser energy density: 407 kJ/cm2.
图 23. 60 W(a)、80 W(b)、100 W(c)、120 W(d)、140 W(e)功率下铜基合金上铜层的表面图像。
图 24. 20 W(a)、30 W(b)、40 W(c)、50 W(d)条件下 304 型铜层的表面图像。
Figure 25. (a) The results of the high-speed camera are superimposed on the laser irradiation trajectory, and (b) the pure copper rod forms a schematic diagram.
Figure 26. (a) Example of a 10× 10 × 10 mm Cu cube constructed using a blue laser (b) Example of a 20 × 20 × 20 mm Cu cube constructed using a blue laser.
Figure 27. Kinetics of melting and solidification of copper samples at 0, 0.1, 0.2, and 0.3 seconds, using (a) a hybrid laser with a 1 kW single-mode fiber laser and a 200 W blue diode laser and (b) a 1 kW single-mode fiber laser.
Figure 28. Effect of the copper sample on (a) a hybrid laser of a 1 kW single-mode fiber laser and a 200 W blue diode laser, and (b) a 1 kW single-mode fiber laser.
Figure 29. Numerical results of infrared laser welding: (a) temperature (K) and fluid flow field of the cross-section of y = 0 mm at t = 0.5 s; (b) absorbed infrared laser power and efficiency; (c) Comparison of infrared laser efficiency.
Figure 30. Top surface topography of laser-clad CuCrZr alloy on AlSi7Mg matrix: infrared laser (a-c), blue laser (d-f), and infrared-blue hybrid laser (gn), where the first power represents the infrared laser power and the second power represents the blue laser power.
Figure 31. The formation mechanism of cladding orbits under different laser sources: infrared lasers (A and B), blue lasers (C and D), high-power infrared + blue lasers (E and F), and low-power infrared lasers + blue light (g and H).
Figure 32. Formation mechanism of pure copper coating on AlSi7Mg matrix irradiated by infrared laser, blue laser and infrared-blue hybrid laser.
Figure 33. Top and cross-sectional morphologies of laser cladding pure copper alloy on AlSi7Mg matrix: infrared laser (a-c), blue laser (d-f) and hybrid laser (g-i).
Key conclusions:
In summary, both green and blue lasers can be used as the first choice, providing a new option for the manufacture of highly reflective metal materials such as copper, and expanding the application field of highly reflective metals such as copper. With the decrease of laser wavelength, the absorption rate of high anti-metal such as copper is significantly improved, which improves the utilization rate and processing efficiency of laser, and makes direct welding of copper possible. The blue-green laser can efficiently and effectively weld highly reflective metals such as copper, while ensuring high quality and repeatability, it can also minimize spatter during the welding process, laying the foundation for obtaining high-quality welds. The blue-green laser can also provide stable heat conduction welding and deep penetration welding, ensuring the consistency of welding penetration. In addition, these lasers have a smaller heat-affected zone, which helps reduce distortion and is ideal for thin plate welding and micro-welding. Minimizing the effects of thermal distortion is critical for additive manufacturing applications in materials such as copper. However, due to the limitation of maximum power and high cost, these lasers are not common in industrial applications. With the advancement of technology, their maximum power has been greatly increased, and the field of application has also expanded. In order to address the limitations of a single laser application, the researchers proposed the concept of laser combination manufacturing. By taking advantage of the advantages of different lasers, the level of device manufacturing can be improved. For example, high-power infrared-blue hybrid lasers in coaxial configurations are expected to address the problem of high metal resistance in alloys and can be extended to crack-sensitive alloys such as TiAl, NiTi, and high-entropy alloys for additive manufacturing. Future technological advancements will lead to more laser combinations and their applications in various fields. For green lasers, as laser technology advances and evolves, it will become more precise and efficient in welding and additive manufacturing. Higher power will also help increase processing speed and productivity. Green lasers exhibit unique advantages on different types of materials, leading to a wider range of applications for materials in laser welding and additive manufacturing. With the growing demand for efficient precision manufacturing in the industry, green laser technology is expected to be more widely used. For blue lasers, the trend is hybrid laser technology, which can be combined with infrared lasers to give full play to their respective advantages and expand their range of applications.
Key messages
Application and development of blue and green laser in industrial
manufacturing: A review
https://doi.org/10.1016/j.optlastec.2023.110202
The copyright of this article belongs to the original author, only for communication and learning, and the final interpretation right belongs to this official account (laser manufacturing research).
Reprinted by Chen Changjun of the Yangtze River Delta G60 Laser Alliance