Influence of rare earth modification and homogenization on the microstructure and mechanical properties of recycled can 3004 aluminum

The microscopic structure of waste can aluminum material was researched by adding Al5TiB refining agent, La-Ce rare earth and mixed rare earth modifiers, and the microstructure and mechanical performance of the modified aluminum material were studied. The experimental results show that the optimal refiner addition amount is 1.1wt%; the material performance can be significantly improved when the content of La-Ce rare earth ranges to a certain degree, but the mixed rare earth barely affects the refinement effect of the aluminum. When being homogenized, the mixed rare earth plays more obvious role in refining the aluminum material than La-Ce rare earth. The optimal plan is modifying the aluminum material with 3wt% mixed rare earth and homogenizing with annealing temperature of 580 ℃, annealing time of 12 hours and heating rate of 5 ℃/min while refining the material with 1.1wt% Al-5Ti-1B.     

复合有机材料激光烧结成型性能试验研究

目的 研究复合有机成型材料激光烧结成型性能。方法 在线扫描激光烧结实验装置上,研究了铺粉厚度、预热温度及激光束参数与复合有机材料激光烧结成型性能的关系。结果 利用实验测量结果,对复合有机材料激光烧结成型性能的影响因素进行了分析。结论 必须合理选择工艺参数,才能得到理想的绕结成型质量。     

钼/铜复合材料快速成型制备工艺研究

提出一种基于快速成型技术的制备钼/铜复合材料的新方法.采用包覆树脂膜低温粉碎研磨制粉的方法,得到了适于选择性激光烧结快速成型用覆膜钼粉;进行了选择性激光烧结成型实验研究,获得优化的工艺参数;开发了高温烧结钼骨架结合渗铜的成型件后处理工艺,得到钼/铜复合材料样件.用扫描电镜(SEM)观察发现,材料中条形钼相组织主要是由多边形的晶粒结合体构成,铜已经与钼紧密结合在一起,形成钼/铜复合材料,其中只有微量孔隙.对材料进行了主要的力学、热学性能测试计算,分别为:常温抗拉强度470 MPa,弹性模量267.8 GPa,延伸率15%,线膨胀系数5.5× 10-6/K.钼/铜复合材料快速制备工艺可应用于兵器弹箭、航空武器等装备的高温零部件和电子工业高电导散热元件的制造.     

覆膜砂选择性激光烧结原型件的后处理试验研究

对铸造覆膜砂的激光快速成型进行了试验研究。系统研究了激光功率、扫描速度、预热温度、铺粉厚度工艺参数对成型试样质量的影响规律,结果获得了铸造用激光快速成型砂型试样。     

包覆不锈钢粉末激光烧结深度的影响因素

制备一种用于激光烧结成形的包覆不锈钢粉末。应用数值模拟预测结合实际测量方法,研究激光功率、激光束扫描速度、预热温度及铺粉密度等参数对激光烧结深度的影响。结果表明,随着预热温度、铺粉密度与激光功率增加,烧结深度增加;随着扫描速度增加,烧结深度降低。但当扫描速度不超过2 mm/s时,烧结深度随扫描速度的增加反而增大。提出一种利用数值模拟预测结果进行激光烧结工艺参数选择的方法。     

Selective laser sintering mechanism of polymer-coated molybdenum powder

A type of polymer-coated molybdenum powder used in selective laser sintering technology was prepared by coating polymer on molybdenum particles and frozen grinding techniques, with the maximum particle diameter of 71 μm. The laser sintering experiments of polymer-coated molybdenum powder were conducted by using the self-developed selective laser sintering machine （HLRP-350I）. The method of microscopic analysis was used to investigate the dynamic laser sintering process of polymer-coated molybdenum powder. Based on the study, the laser sintering mechanisms of polymer-coated molybdenum powder were presented. It is found that the mechanism is viscous flow when the laser sintering temperature is between 100 ℃ and 160 ℃, which can be described by a two-sphere model; and the mechanism is melting/solidification when the temperature is above 160 ℃.     

Numerical simulation of temperature field during selective laser sintering of polymer-coated molybdenum powder

The technology of length-alterable line-scanning laser sintering was introduced. Based on the research of laser heating property, powder thermal physics parameters and laser sintering process, a numerical model of the temperature field during length-alterable line-scanning and laser sintering of polymer-coated molybdenum powder was presented. Finite element method （FEM） was used to simulate the temperature field during laser sintering process. In order to verify the simulated results, a measuring system was developed to study the laser sintering temperature field. Infrared meter was introduced to measure the surface temperature of sintering powder; the temperature of its inside part was measured by thermocouple. The measured results were compared with the numerical simulation results; the conformity between them is good and the relative error is less than 5%.     

赝复体原型件的后处理及石膏模的制作

介绍了赝复体原型件的后处理工艺.采用石膏型精密铸造与RP技术相结合的方法,制造出硅胶赝复体.对石膏型浆料配方和石膏浆料真空搅拌及灌浆工艺参数进行优化.提出脱蜡模的方法及脱模后石膏型的低温烘干及高温焙烧工艺.     

精铸蜡粉激光烧结成型工艺试验研究

研制开发了精铸蜡粉,采用正交试验方法研究了其激光烧结性能和烧结成型工艺,在此基础上得到了激光烧结成型最佳工艺参数,制作了合格的精铸蜡模,并结合精密铸造工艺得到了金属铸件。试验结果表明：自主开发的精铸蜡粉具有良好的烧结成型性能,铸造工艺适应性好,可用于精铸蜡模的快速制造。     

激光熔覆原位合成TiC/Al陶瓷基复合涂层增强Ti6Al4V研究

采用Ti-C-Al体系激光点火自蔓延合成TiC/Al材料的同时,在Ti6Al4V钛合金表面形成均匀厚度的涂层。实验所用设备为2kWNd:YAG脉冲固体激光器;原料中钛碳原子比1:1,铝含量范围10%~40%(质量分数)。原料中的铝含量对原位合成的TiC颗粒形态和大小影响较大,通过实验确定了原料中合适的铝含量。利用扫描电镜对涂层与基体结合界面微观结构进行表征,测试涂层的显微硬度和耐磨性。结果表明,涂层和基体有良好的冶金结合;TiC颗粒在涂层表面处主要以树枝晶状存在,而在涂层与基体连接处主要为近球状晶粒;涂层显微硬度可达到8000MPa(HV0.5),约为基材的2~3倍。