Effect of Post Treatment on the Microstructure and Properties of the GH3536 Alloy Formed by Additive Manufacturing
Xiao Lairong, Tan Wei, Liu Liming, Wang Huan, Peng Zhenwu, and Zhao Xiaojun
Selective laser melting was used to fabricate a GH3536 alloy. The effects of hot isostatic pressing (HIP) and solution treatment (ST) on the microstructure, mechanical properties, and fatigue crack growth properties of the GH3536 alloy were investigated. The results show that there are molten pool, columnar grains, dendrites, holes, and cracks in the as-deposited alloy. The HIP process can effectively heal defects, eliminate molten pools and dendrites, and make all grains grow into equiaxed grains. Besides, it can lead to the continuous precipitation of carbides along the grain boundary. After ST, many carbides dissolve back into the matrix. The tensile strength, hardness, and elongation of the as-deposited alloy are 782.1 MPa, 227.9 HV, and 17.7%, respectively, and defects are essential factors affecting the plasticity. After the HIP process, the strength and hardness of the alloy decrease to 693.7 MPa and 170.4 HV, and its elongation increases to 34.7%. After the ST process, the strength, hardness, and elongation of the alloy increase to 741.0 MPa, 180.6 HV, and 48.7%, respectively. In comparison, the fatigue crack growth resistance of the as-deposited alloy is less than that of the alloy after HIP and ST are improved.
  • Sep. 14, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 17 1714010 (2021)
  • DOI:10.3788/LOP202158.1714010
Effect of Pulse Times on Texture Morphology under Millisecond Laser
Chen Cheng, Hua Xijun, Zhu Dongpo, Xu sheng, and Xie xuan
In order to explore the evolution law of the texture morphology under the action of multi-pulse millisecond laser, a two-dimensional symmetric model is established in this paper, which considered the influence of recoil pressure, surface tension, and evaporation rate on the change of molten pool, and is used to analyze the evolution law of the texture morphology and carry out experimental verification. The results show that under the action of recoil pressure, the depth and diameter of the pit increase with the increase of the number of pulses. The central bulge and the edge bulge are related to the thermal capillary force and Laplace pressure, and the height of bulge decreases with the increase of the number of pulses. At the edge of the molten pool, the molten material flows to the center under the influence of the thermal capillary force, and the height of the edge bulge decreases with the increase of the number of pulses.
  • Sep. 14, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 17 1714009 (2021)
  • DOI:10.3788/LOP202158.1714009
Joint Microstructure and Properties of D36 Steel Using Narrow Gap Laser Welding
Chai Xutian, Yin Yan, Wang Zhipeng, Dong Kaiji, Li Zhihui, and Zhang Ruihua
The low-alloy and high-strength steel D36 is joined by narrow-gap laser wire-filled welding, which results in good multi-layer and multi-pass thick plate welding without cracks, pores, and other defects after welding. The microstructure and mechanical properties of the welded joints are analyzed by the tension and bending test, microhardness test, microstructure observation, and other analytical methods. The results show that the coarse-grained heat-affected zone consists of a large number of lamellar martensite, and the microstructure of the fine-grained zone is composed of the fine-grained pearlite and ferrite. The weld center structure is proeutectoid ferrite + acicular ferrite + granular bainite. The regions with filler wire weld bead hardness in order from high to low is heat affected zone, weld center, and base material. The regions with laser primer welding hardness in order from high to low is weld center, heat affected zone, and base metal. The tensile specimens of the welded joints all fractured at the base metal position. The fracture is at an angle of 45° with the force direction, and there is obvious necking, which is a typical ductile fracture. The average tensile strength of the welds is 537 MPa, and the average elongation after fracture is 15.6%.
  • Sep. 14, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 17 1714008 (2021)
  • DOI:10.3788/LOP202158.1714008
Selective Laser Melting Technology Applied into Aircraft Air Inlet Protective Grilling
Cai Xiaoye, Hu Jiaqi, Cheng Zonghui, and Zhang Jie
In this study, selective laser melting (SLM) technology was used to produce test samples and aircraft air inlet protective grilling using TC4 powders. The microstructures and mechanical properties of printed samples were further analyzed. Results indicate that the cross section of fractured longitudinal samples has a fine microstructure, which leads to a strong fine-grain strengthening effect. Thus, superior comprehensive mechanical properties of the longitudinal samples are achieved. Moreover, the microstructure of the printed samples is found to comprise fine acicular α’ martensite. After annealing, the α’ martensites almost completely disappear. A new mixed microstructure comprising packets of the Widmannstatten and basket-weave microstructures is formed. The as-annealed samples possess high ductility and toughness with relatively inferior strength. In addition, the mechanical properties of as-annealed samples are equivalent to those of the as-forged ones. Based on the above-mentioned experimental results, the aircraft air inlet protective grilling of TC4 was prepared via SLM. The dimension precision of the unit grids is better than ±0.1 mm. Moreover, the manufacturing periodicity is reduced from seven to four days.
  • Sep. 14, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 17 1714007 (2021)
  • DOI:10.3788/LOP202158.1714007
Compressive Properties and Numerical Simulation of Porous Structure Fabricated by Laser Powder Bed Fusion
Chen Runping, Zhang Dongyun, Hu Songtao, Xu Yangli, Huang Tingting, Zhang Long, and Liu Zhiyuan
The human bone appears as a hierarchical structure composed of cortical bone with high density and strength and cancellous bone with low density and blood vessels. Therefore, the structure and mechanical properties of human implants should match the characteristics of human bone. Based on the stress on the natural human bone, the titanium alloy porous structure designed by topology optimization method was fabricated by laser powder bed fusion (LBPF). The mechanical properties and deformation failure mode of the porous structure were analyzed by compression experiment and numerical simulation. It was found that the numerical simulation and experimental results have a high consistency in the current work. Finally, by comparing with the mechanical properties of human natural bone, combined with the failure mode of porous structure, a porous material suitable for human implants was obtained.
  • Sep. 14, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 17 1714006 (2021)
  • DOI:10.3788/LOP202158.1714006
Effect of Magnetic Field on Friction and Wear Properties of Laser Surface Textured
Li Yi, Yu Aibing, Chen Qiujie, and Zhao Shuo
Surface texture treatment can improve the wear properties of the materials. Laser processing technology is often used for the preparation of surface texture of various materials because of its advantages of high precision and high efficiency. With the development of electromagnetic technology, more friction pairs serve in magnetic field environment. In order to analyze the effect of applied magnetic field on the friction and wear of the dimple textured surface, the dimple texture is fabricated with laser on the surfaces of the 45# steel specimens, and wearing experiments are carried out under two experimental conditions, such as normal and applied magnetic field. Coefficient of friction, lubricating oil viscosity and wear mass loss of the worn specimens are measured. Worn surfaces and wear debris are observed with microscope. The experimental results show that under oil-lubricated conditions, applied magnetic field reduces the coefficient of friction, wear mass loss and adhesive wear on laser textured surface. Applied magnetic field can improve the oil viscosity, the capacity of trapping wear debris of textured dimples and the carrying capacity of oil film, which can improve the tribological properties of the laser dimple textured surface.
  • Sep. 14, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 17 1714005 (2021)
  • DOI:10.3788/LOP202158.1714005
Beam Pointing Stability of Extreme Ultraviolet Lithography Light Source System
Li Xinpeng, Yu Deyang, Pan Qikun, Zhang Ranran, Zhang Kuo, Guo Jin, and Chen Fei
A beam alignment system for extreme ultraviolet lithography light source system is designed to meet the requirement of beam pointing stability of extreme ultraviolet lithography light source system and ensure the conversion efficiency of extreme ultraviolet light. The alignment system is composed of two parts, the beam jitter detection module and the beam alignment module. By analyzing the beam jitter mechanism and beam control principle, a closed-loop alignment system with detection and control is built based on the virtual instrument development software LabVIEW. The experimental results show that after the beam passes through the alignment system, the jitter amplitude in the horizontal direction is less than 2 μm, the jitter amplitude in the vertical direction is less than 4 μm, and the pointing stability is less than 6 μrad, which meets the requirements of the light source system for the beam pointing stability.
  • Sep. 14, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 17 1714004 (2021)
  • DOI:10.3788/LOP202158.1714004
Experimental Study on Time-Delay Characteristic and Effective Bandwidth for Chaotic Semiconductor Lasers
Liu Pengbo, Zhang Shenghai, Wei Zhengtong, Wu Tian'an, Zhang Xiaoxu, and Chen Wenbo
The time-delay characteristic and effective bandwidth of semiconductor lasers produced by dual modulation of external optical injection and feedback are numerically and experimentally investigated. The experimental results show that the dual-modulated laser system has large bandwidth, and the time-delay characteristic is weakened compared with the single-modulated laser system. The experimental results have been compared to verify the obtained numerical results, indicating that the proposed scheme can improve the security performance of chaotic laser-based secure communication. Besides, more effective bandwidth and less time-delay characteristic can be obtained in the negative frequency-detuning region. The delay characteristic suppression will deteriorate in the positive frequency-detuning region.
  • Sep. 14, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 17 1714003 (2021)
  • DOI:10.3788/LOP202158.1714003
Effect of Energy Density on Surface Morphology and Properties of H13 Mold Steel via Picosecond Laser Cleaning
Peng Wei, and Lei Hui
  • Sep. 14, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 17 1714002 (2021)
  • DOI:10.3788/LOP202158.1714002
Femtosecond Laser Ablation Kinetic Energy Thermal Model and Tooth Surface Topography of Face Gear Materials
Xiao Yongbo, Ming Rui, Lai Mingtao, Li Xuekun, Ma Yulong, and Ming Xingzu
Femtosecond laser microcorrection technology is a new type of processing method that uses a laser with ultrashort pulse-width and high energy density to micromachine the gear tooth surface. Considering the mutual temperature induction between the components of the gear material, a kinetic energy thermal model of the femtosecond laser-ablated surface gear material was established, and the evolution of the temperature field of the tooth surface of the femtosecond laser-modified surface gear was simulated and analyzed. The temperature of electrons rises sharply and is much greater than the lattice temperature and the depth and diameter of ablation pits increase. The tooth surface morphology of the ablated pits was experimentally observed, confirming the correctness of the kinetic energy thermal model, and providing theoretical guidance for the study of femtosecond laser-ablated surface gears.
  • Sep. 14, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 17 1714001 (2021)
  • DOI:10.3788/LOP202158.1714001