Author Affiliations
1State Key Laboratory of Precision Welding & Joining of Materials and Structures, Harbin Institute of Technology, Harbin 150001, Heilongjiang , China2Beijing Remote Sensing Equipment Research Institute, Beijing 100854, Chinashow less
Fig. 1. Lens tube shape structure for optical systems
Fig. 2. Particle size distribution and surface morphology of the optimized powder. (a) Particle size distribution curve; (b) statistical image of powder sphericity; (c) surface morphology of the powder
Fig. 3. SLM process test results. (a) Optimized powder spreading effect; (b) product surface quality
Fig. 4. Microscopic morphology of Invar alloy samples formed at different scanning intervals. (a)(c)(e)(g) Horizontal; (b)(d)(f)(h) vertical
Fig. 5. Microscopic morphology of Invar alloy samples formed at different scanning velocities. (a)(c)(e)(g) Horizontal; (b)(d)(f)(h) vertical
Fig. 6. Stress and strain simulation results of Invar alloy lens tubes. (a) Stress simulation of the original model; (b) strain simulation of the original model; (c) stress simulation of the model after topology optimization; (d) strain simulation of the model after topology optimization
Fig. 7. Optimization of the lens tube model, as well as stress and strain simulation after optimization. (a) Printing support of the original model; (b) printing support of the optimized model; (c) stress and strain simulation results after process optimization
Fig. 8. Invar alloy lens tube and test rods manufactured by SLM process. (a) Lens tube; (b) fracture location of the test rods; (c) test robs before and after thermal expansion test
Fig. 9. Three-dimensional scanning of the lens tube and structural deviation measurement results
Fig. 10. X-ray inspection results of Invar alloy tube. (a) X-ray scanning image; (b)–(f) residual stress detection points
Element | Mass fraction /% |
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C | 0.01 | S | 0.008 | P | 0.008 | Si | 0.018 | Mn | 0.8 | Ni | 34.29 | O | 0.888 | Fe | 63.97 |
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Table 1. Chemical composition of Invar alloy powder
Element | Mass fraction /% | Standard /% |
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C | 0.006 | 0.05 | S | 0.006 | 0.02 | P | 0.01 | 0.02 | Si | 0.01 | 0.3 | Mn | 0.35 | 0.2‒0.6 | Ni | 35.25 | 35‒37 | O | 0.034 | 0.05 | Fe | 64.33 | 63‒65 |
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Table 2. Chemical composition of the optimized Invar alloy powder
Physical property | Value | Standard |
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Mobility /(s/50 g) | 14.7 | 16 | Apparent density /(g/cm3) | 4.71 | 4.2 | Tap density /(g/cm3) | 5.2 | 5.8 | Sphericity | 0.89 | 0.85‒0.9 | Particle size (D10) /μm | 17.4 | 15‒25 | Particle Size (D50) /μm | 32 | 30‒40 | Particle size (D90) /μm | 56.4 | 50‒60 |
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Table 3. Physical properties of the optimized Invar alloy powder
No. | Power /W | Scanning velocity /(mm/s) | Scanning interval /mm | Thickness /mm | Lap width /mm | Energy density /(J/mm3) |
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1 | 370 | 1000 | 0.08 | 0.04 | 0.14 | 114.6 | 2 | 370 | 1000 | 0.09 | 0.04 | 0.14 | 102.78 | 3 | 370 | 1000 | 0.10 | 0.04 | 0.14 | 92.5 | 4 | 370 | 1000 | 0.11 | 0.04 | 0.14 | 76.45 |
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Table 4. Setting of SLM parameters
No. | Power /W | Scanning velocity /(mm/s) | Scanning interval /mm | Thickness /mm | Energy density /(J/mm3) | Tensilestrength /MPa | Yieldstrength /MPa | Elongation /% | Shrinkagerate /% |
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1 | 370 | 900 | 0.09 | 0.04 | 114.2 | 482 | 388 | 29 | 73 | 2 | 370 | 1000 | 0.09 | 0.04 | 67.5 | 468 | 368 | 29 | 64 | 3 | 370 | 1100 | 0.09 | 0.04 | 67.3 | 435 | 354 | 35 | 73 | 4 | 370 | 1200 | 0.09 | 0.04 | 91.0 | 440 | 361 | 33 | 73 |
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Table 5. SLM parameters and mechanical property test results
No. | Tensile strength /MPa | Yield strength /MPa | Elongation /% | Shrinkage rate /% | CTE /K |
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1 | 455 | 364 | 36 | 79 | 1.910-6 | 2 | 451 | 362 | 33.5 | 80 | 1.910-6 | 3 | 467 | 375 | 35 | 80 | 1.810-6 |
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Table 6. Mechanical properties of the test bars after heat treatment