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941.
使用电磁搅拌、变质处理及其复合工艺分别成功制备了过共晶Al-20Si半固态浆料,研究了电磁搅拌和变质的复合作用对过共晶Al-20Si合金中初生Si长大和形貌的影响。研究结果表明:复合作用可以获得比单种变质处理和电磁搅拌的过共晶Al-20Si合金更加细小、更加圆整的初生Si组织。复合作用获得的初生硅比单一处理尺寸平均减小25.19%,圆整度平均提高8.40%。而且共晶Si组织也得到球化。复合作用细化组织的机理为:变质后施加旋转磁场,促进了变质剂的扩散,更多的初生Si与共晶Si组织相互打碎,深化了变质和电磁搅拌效果,细化显微组织。 相似文献
942.
The pressing bonding of steel plate to QTi3.5-3.5graphite slurry was studied. The bonding conditions were 620℃ for preheating temperature of steel plate, 530℃ for preheating temperature of dies, 50 MPa for pressure and 2 min for pressing time. The relationship between the solid fraction of QTi3.5-3.5graphite slurry and the interracial mechanical property of bonding plate was obtained. The results show that when the solid fraction of QTi3.5-3.5graphite slurry is smaller than 45.8%, the interracial shear strength of bonding plate increases with the increasing of solid fraction. When the solid fraction is larger than 45.8%, the interracial shear strength decreases with the increasing of solid fraction. When the solid fraction is 45.8%, the largest interracial shear strength of bonding plate 127 MPa can be got, and the interface is made up of Fe-Cu solid solution. 相似文献
943.
分析了气膜片零件胀形质量差的原因,对原模具结构进行了改进,解决了原模具成形后贴模不理想、型面不准确的问题,提高了零件质量。 相似文献
944.
945.
946.
In this study, a large ceramic part was successfully compacted and sintered using uniaxial die compaction technique. The effects of die design, compaction pressure, lubrication, sintering procedure and part orientation in the oven on the P/M part quality were investigated and the preferred process conditions were discussed and concluded. The main quality issues encountered were cracking and distortion. A finite element model for the powder compaction process was also developed and validated. Based on the model, the relationship between the cracking location and the density distribution predicted from finite element analysis (FEA) was discussed. 相似文献
947.
948.
Li Peng Ji Shengqin Zeng Xiaoyan Hu Qianwu Xiong Weihao 《International Journal of Machine Tools and Manufacture》2007,47(6):996-1002
Direct laser fabrication (DLF) is an advanced manufacturing technology, which can build full density metal parts directly from CAD files without using any modules or tools. The investigation on the fabrication of thin-walled parts of nickel alloy using open-loop DLF process is introduced in this paper. The experimental setup consisted of a CO2 laser, a 3-axis CNC table, a coaxial powder nozzle and a powder recycler. The 3D-CAD file of a thin-walled metal part was converted into the STL file format and imported into software HUST-RP to generate ‘pseudo-random’ scanning paths of laser beam. The influence of process parameters on the build height of thin-walled metal parts was studied by 1–10 layered single-bead stacks of nickel alloy. The result shows that the interference factors which affect the build height of thin-walled metal parts occur randomly during the process. For open-loop DLF process, thin-walled metal parts can achieve much better shape quality if the process parameters are suitable. Multilayer single-bead walls were built up with different scanning velocity to obtain the optimal process parameters of thin-walled parts of nickel alloy. It shows that thin walls of nickel alloy with uniform height can be built up layer by layer in a certain range of specific energy. However, it is difficult to control the build height of complex thin-walled metal parts in an accurate manner just using optimal parameters. A special coaxial powder nozzle was designed in this paper. In a certain range, the deposition thickness of the nozzle is nearly linearly increased with increase in the standoff distance between the powder focusing point of the nozzle and the deposition substrate. By means of the nozzle, a novel method to control the build height of thin-walled metal parts using open-loop DLF process was introduced. The difference in build height of a thin-walled part can be compensated automatically in one or several layers during the process. It is proved that the build height of a thin-walled metal part can be accurately controlled in theory using the nozzle. A complex single-bead part of nickel alloy whose geometry was designed to be the well-known Chinese ‘FU’ was fabricated and explained in this paper. The result shows that the shape quality of the sample is quite good, and actual build height of the sample is 53.54 mm while the designed value is 54 mm. 相似文献
949.
研究了Mg-Li-Zn-Zr镁合金和添加钇、镧错铈混合稀土的Mg-Li-Zn-Zr-Y-LPC镁合金的显微组织和力学性能特点.以及热处理对两种镁锂合金显微组织和力学性能的影响规律。结果表明:铸态Mg-7.13Li-3.92Zn-1Zr合金主要由α-Mg相.θ′相(MgLi2Zn)组成;添加混合稀土后,铸态Mg-8.16Li-4.10Zn-2.86Y-0.59Zr-2.14LPC合金主要由Li、Zn和RE在Mg中的固溶体和Mg-Li-Zn-RE块状化合物共同组成。对铸态Mg-Li-Zn-Zx合金均化处理后,合金的θ′相转变为更为稳定的θ相(MgLiZn),并且均化处理可以明显提高铸态Mg-7.13Li-3.92Zn-1Zt合金的力学性能。另外,氢化处理也可以明显提高铸态Mg-Li-Zn-Y-Zr-LPC合金的力学性能。 相似文献
950.