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为获得最佳设计方案,设计两种实验方案,通过改变工艺参数对铜钛合金复合材料进行激光金属沉积。从显微组织演变、硬度和力学性能三方面对所沉积的复合材料进行表征。结果表明:复合材料的显微组织由一次、二次和三次枝晶臂,针状组织和α+β共晶组织组成。两种实验方案结果表明,在激光功率为1200 W、扫描速率为1.2 m/min的条件下得到的样品E具有最高的硬度,其值为HV (190±42),但由于其脆性,因此出现一些横间裂纹;而在激光功率为1200 W、扫描速率为0.3 m/min条件下得到的样品B无裂纹产生,且其显微组织良好并含有较多的枝晶。得到的铜复合材料的应变硬化系数为3.35。  相似文献
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A method of laser-activated deposition through the metabolite of Acidithiobacillus ferrooxidans is demonstrated. The experimental results indicate that the deposition process exhibits positive correlation to laser power and a negative correlation to scanning speed. The amount of deposition is related to the supplied energy per unit length of laser scanning. With respect to the thermal field on the substrate produced by a moving point source and a laser beam crossing a reference point, the temperature history and the accumulated energy are used to model the deposition process. The threshold temperature of the deposition is estimated 500 K, and the activation energy per unit volume of deposition of the process is about 120 pJ/μm3.  相似文献
3.
The use of porous surface structures is gaining popularity in biomedical implant manufacture due to its ability to promote increased osseointegration and cell proliferation. Laser direct metal deposition (LDMD) is a rapid manufacturing technique capable of producing such a structure. In this work LDMD with a diode laser in continuous mode and with a CO2 laser in pulsed modes are used to produce multi-layer porous structures. Gas-atomized Ti-6Al-4V and 316L stainless steel powders are used as the deposition material. The porous structures are compared with respect to their internal geometry, pore size, and part density using a range of techniques including micro-tomography. Results show that the two methods produce radically different internal structures, but in both cases a range of part densities can be produced by varying process parameters such as laser power and powder mass flow rate. Prudent selection of these parameters allows the interconnected pores that are considered most suitable for promoting osseointegration to be obtained. Analytical models of the processes are also developed by using Wolfram Mathematica software to solve interacting, transient heat, temperature and mass flow models. Measured and modelled results are compared and show good agreement.  相似文献
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Based on the element life and death theory of finite element analysis(FEA), a three-dimensional multi-track and multi-layer model for laser metal deposition shaping(LMDS) was developed with ANSYS parametric design language(APDL), and detailed numerical simulations of temperature and thermal stress were conducted. Among those simulations, long-edge parallel reciprocating scanning method was introduced. The distribution regularities of temperature, temperature gradient, Von Mise's effective stress, X-directional, Y-directional and Z-directional thermal stresses were studied. LMDS experiments were carried out with nickel-based superalloy using the same process parameters as those in simulation. The measured temperatures of molten pool are in accordance with the simulated results. The crack engendering and developing regularities of samples show good agreement with the simulation results.  相似文献
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Measuring temperatures in the material during laser metal deposition (LMD) has an inherent challenge caused by the laser. When thermocouples are radiated by the high intensity laser light overheating occurs which causes the thermocouple to fail. Another identified difficulty is that when the laser passes a thermocouple, emitted light heats the thermocouple to a higher temperature than the material actually experience. In order to cope with these challenges, a method of measuring temperatures during LMD of materials using protective sheets has been developed and evaluated as presented in this paper. The method has substantially decreased the risk of destroying the thermocouple wires during laser deposition. Measurements using 10 mm2 and 100 mm2 protective sheets have been compared. These measurements show small variations in the cooling time (∼0.1 s from 850°C to 500°C) between the small and large protective sheets which indicate a negligible effect on the temperature measurement.  相似文献
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Laser-based direct metal deposition (DMD) is a solid freeform fabrication process capable of fabricating fully dense and metallurgically sound parts. The process has been greatly enhanced toward multi-directional deposition by the use of discontinuous radially symmetrical powder nozzles to supply the build material. Since many operational parameters depend on the gas–powder stream characteristics between the nozzles and the deposition point, an extensive understanding of the gas–powder flow is necessary. Three-dimensional (3D) multi-phase gas–powder flow structures of radially symmetrical nozzles are modeled using computational fluid dynamics methods. The obtained results are in good agreement with the experimental ones, and they provide a good insight into the process phenomena.  相似文献
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李俐群  曲劲宇  王宪 《表面技术》2019,48(6):332-337
目的 研究激光熔化沉积AlSi10Mg铝合金的成形特性及力学性能。方法 以颗粒度45~105 μm的AlSi10Mg粉末为材料,6061铝合金为基板,利用光纤激光器在充氩舱内分别进行单层单道、竖直薄壁单墙体与倾斜薄壁墙体的成形试验。测试单墙体的抗拉强度与延伸率,并通过扫描电子显微镜和光学显微镜对微观组织形貌进行分析。结果 单层单道沉积层高度与激光扫描速度负相关,与送粉速度成线性正相关;而沉积层宽度与扫描速度负相关,与激光功率正相关。沉积单墙体时,沉积前10层最不稳定,墙体厚度低于后续层的厚度。为了使沉积过程稳定,墙体不塌陷,通过激光功率在前20层左右逐层递减,成功制备出250层(高10 cm)以上的单墙体。工艺选取合适时,AlSi10Mg具有良好的成形能力,激光头角度保持竖直不变,墙体倾角60°以下可以稳定沉积。制备沉积态AlSi10Mg气孔率约3%,抗拉强度250 MPa左右,延伸率5%以上,抗拉强度高于成分相似的ZL104铸件25%。微观组织内Al-Si共晶细小,没有针片状共晶组织,并且组织沿沉积方向呈现周期性变化。结论 AlSi10Mg在激光熔化沉积时具有良好的成形能力,沉积态的组织强度高于铸态组织强度。优化后的工艺可以稳定沉积制备下圆上方的变截面薄壁样件。  相似文献
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