Novel titanium particles reinforced Zr-based bulk metallic glass composites prepared by infiltration casting

A novel Ti /Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 composite was successfully prepared by infiltrating the melt into sintered Ti preform. It shows that the introduction of Ti particles into the composite results in an increase in elastic strain to 3% and an enhancement of the strength up to 2.1 GPa. High specific strength has been obtained because of the decrease in density of the composite. It is suggested that an improvement in the mechanical properties of the composite may be attributed to the generation of multiple shear bands and some deformation in the Ti particles.     

铸渗法制备金属基表面复合材料的研究进展及应用

铸渗技术是近年来发展起来的一种制备金属基表面复合材料的新技术.综述这项技术在金属铸渗机理、铸渗工艺方法及其影响因素等方面的研究及应用概况,阐述铸渗法制备金属表面耐磨复合材料的制备工艺方法、铸渗机理和铸渗组织的新进展,总结了新近开发的一些改善铸渗效果的工艺措施,并指出了该项技术目前还存在的若干问题,并对其今后的发展方向进行了展望.同时为金属基表面复合材料的制备、选择和开发提供新思路.     

Thermal properties of open-celled aluminum foams prepared by two infiltration casting methods

Contrastive research was carried out to study the thermal properties of open-celled aluminum foams prepared by counter-gravity infiltration casting system and the traditional process respectively.The experimental results show that the thermal conductivity coefficients of aluminum foams prepared by two different infiltration methods have similar increasing trend with the increase of particle size; along with the reducing porosity,the thermal conductivity coefficients will be enhanced oppositely.However,with the same particle size,the open-celled aluminum foam prepared by the former method has a higher thermal conductivity coefficient obviously.It is largely because that the sample prepared by counter-gravity infiltration casting has a lower void content and better dense crystallization of metal-matrix after the constant pressure process.     

汽车进气歧管真空注型材料选用和工艺探讨

以塑料替代铝合金制造汽车发动机进气歧管是目前汽车工业的重点研发内容,对于汽车轻量化及提高发动机性能和燃料利用率有重要作用。在塑料发动机进气歧管设计开发阶段,采用真空注型工艺进行少量试制件生产并进行性能试验和设计验证,试制件除了对制件有尺寸精度、形位精度要求外,还对材料的耐高温及气密性有特殊要求。通过对选用材料和常用材料的对比试验,确定了材料和工艺,并经过汽车发动机耐久性试验,符合开发阶段的试验要求。研究结果对同类产品开发有参考价值,目前此项研究仅局限于进气歧管的开发阶段。     

Preparation and arc erosion resistance of Cf/Cu composite by vacuum melting infiltration

Cf/Cu composite was prepared by vacuum melting infiltration. Ti and Cr were doped to the Cu alloy to improve the wettability between Cu and carbon. The microstrueture was investigated by XRD, SEM and EDS. The arc erosion rate of Cf/Cu composite was investigated in vacuum. The results showed that the Ti and Cr could improve the wettability between Cu and C/C preform and the infiltration ability of Cu into C/ C preform greatly. A TiC interface formed between the fibers and matrix. The good bonding between the fiber and matrix guaranteed that part of the Cu matrix can still be bonded on the fibers even when the material was exposed to the plasma. Consequently, the carbon fibers were protected from the erosion. In comparison, Cu was completely consumed by the arc erosion. Hence, the graphite was eroded and presented a cauliflower-like morphology. Therefore, the prepared C/Cu bad better ability to resist the arc erosion, compared with common Cu-C material.     

Effects of parameters on formation and microstructure of surface composite layer prepared by lost foam casting technique

Surface composite layer was fabricated on the AZ91D substrate using the lost foam casting (LFC) process. The pre-coating layer reacted with melt substrate and formed the composite layer, and the coating was mainly consist of alloying aluminum powder and low-temperature glass powder (PbO-ZnO-Na2O). The vacuum degree, pouring temperature, mold filling process of melt, and pre-coating thickness played an important role during the formation process of composite layer. The results show that surface morphology of composite layer can be divided into three categories: alloying effect of bad and good ceramic layer, alloying effect of good and bad ceramic layer, composite layer of good quality. The main reason for bad alloying layer is that alloying pre-coating thickness is so thin that it is scoured easily and involved in the melt, in addition, it is difficult for melt to infiltrate into the alloying coating owing to the surface tension of coating when the vacuum degree is excessively low. Bad ceramic layer is because of somewhat lower pouring temperature and the thicker alloying coating, due to the absorption of heat from the melt, making low temperature glass powder pre-coating layer fuse inadequate. Thus, to get good quality composite layer, the process conditions must be appropriate, the result shows that the optimum process parameters are as follows: at a pouring temperature of 800 ℃, vacuum degree of -0.06 MPa, alloying pre-coating thickness of 0.4 mm, and low glass powder pre-coating layer thickness of 1 mm.     

Microstructure and mechanical properties of AZ31 alloy ingot fabricated by semi-continuous casting

The AZ31 alloy ingot with diameter of 110 mm and length of 3500 mm was fabricated successfully. The compositions and microstructure morphologies of the ingot at different locations were performed, which indicated that the chemical composition distributed homogeneously through the whole alloy ingot and the average grain size increased from the surface to the center. The results of the EDS and element face-scanning illustrated that the eutectic compounds mainly consisted of fl-Mg17Al12 and a small amount of fl-Mgl7（AlZn）12. Furthermore, slight improvements of the strength and ductility were observed from the center to the surface along the axial direction of the alloy ingot, while both the strength and elongation to failure of the samples along the radial direction are higher than that along the axial direction. The fine grain strengthening was the main contributors to the strength of the as-casted AZ31 alloy.     

Bonding mechanism of X10CrNi18-8 with Ni/Al_2O_3 composite ceramic by pressureless infiltration

An alloy steel/alumina composite was successfully fabricated by pressureless infiltration of X10CrNi18-8 steel melt on 30%(mass fraction) Ni-containing alumina based composite ceramic(Ni/Al2O3) at 1 600 ℃.The infiltration quality and interfacial bonding behavior were investigated by SEM,EDS,XRD and tensile tests.The results show that there is an obvious interfacial reaction layer between the alloying steel and the Ni/Al2O3 composite ceramic.The interfacial reactive products are(FexAly)3O4 intermetallic phas...     

Design,preparation,and structure of particle preforms for Si_3N_(4(P))/Si_3N_4 radome composites prepared using chemical vapor infiltration process

A particle preform was designed and prepared by conglomerating and cold-pressed process,which was condensed by chemical vapor infiltration(CVI)process to fabricate silicon nitride particles reinforced silicon nitride composites.The conglomera- tions are of almost sphericity after conglomerated.There are large pores among the conglomerations and small pores within them- selves in the preform according to the design and the test of pore size distribution.The pore size of the preform is characterized by a double-peak distribution.The pore size distribution is influenced by conglomeration size.Large pores among the conglomerations still exist after infiltrated Si_3N_4 matrix.The conglomerations,however,are very compact.The CVI Si_3N_4 looks like cauliflower- shaped structure.     

Preparation and properties of multi-wall carbon nanotube/SiC composites by aqueous tape casting

MWCNTS/SiC composites were fabricated by aqueous tape casting. High solid content (50 vol%) SiC slurries with sintering additives and multi-wall carbon nanotubes (MWCNTs) as reinforcements were prepared using Tetramethylammonium hydroxide as the dispersant. The stability of MWCNTs/SiC slur-ries was studied and characterized in terms of zeta potential and rheology measurements. The relative density of the composite was about 98% after hot-pressing at 1850℃ (at 25 MPa in Ar for 30 min). The hardness of the composites decreased with the increase in MWCNTs content. The flexural strength and the fracture toughness were 742.17 MPa and 4.63 MPa·m1/2, respectively when the MWCNTs content was 0.25 wt%. Further increase in MWCNTs content to 0.50 wt% did not lead to the increase in mechanical properties. Most of MWCNTs were found to be located at SiC grain boundaries and the pull out of the MWCNTs was observed.     

Microstructure of Ni / WC surface composite layer on gray iron substrate

The surface infiltrated composite (Ni/WC) layers on gray iron substrate were fabricated through a vacuum infiltration casting technique (VICT) using Ni-based composite powder with different WC particles content as raw materials.The microstructures of surface infiltrated composite layer,the interface structures between surface composite layer and the substrate,the changes of macro-hardness with the increasing of WC content and the micro-hardness distribution are investigated.The infiltrated composite layer includes a surface composite layer and a transition layer,and the thickness of the transition layer decreases with the increasing content of WC.The thickness of transition layer with 20%WC content in the surface infiltrated composite layer was 170 μm which was the thickest for all transition layers with different WC content.The surface composite layer was mainly composed of WC,W2C,FeB and NiB,along with Ni-Cr-Fe,Ni (Cr) solid solution,Ni (Si) solid solution and Ni (Fe) solid solution.The transition layer was composed of Ni (Cr) solid solution,Ni (Fe) solid solution,Ni (Si) solid solution,Fe (Ni) solid solution and eutectic.The surface macro-hardness and micro-hardness of the infiltrated layer had been evaluated.The macro-hardness of the surface composite layer decreases with the WC content increasing,and the average macro-hardness is HRC60.The distribution of micro-hardness presents gradient change.The average micro-hardness of the infiltrated layer is about HV1000.     

铸造氧化铝短纤维增强铝合金复合材料的研究

本文在国产氧化铝短纤维的基础上,研究了铸造氧化铝短纤维增强铝合金复合材料。研究结果表明,用挤压铸造技术制备氧化铝短纤维增强铝合金复合材料是可行的,和基体合金相比,所制备的复合材料具有良好的显微组织和优异的机械性能。     

三维机织复合材料预制件结构优选CAD

探讨了三维机织复合材料预制件结构的多样性，针对预制件结构难以选择的问题，采用模糊数学多指标综合评判法，编制了三维机织复合材料预制件结构CAD软件，得到了令人满意的结果。这一软件可解决三维机织复合材料预制件结构的优化问题，为复合设计人员提供了一个方便、快速的辅助设计环境。     

Fabrication and properties of Al matrix composites strengthened by in situ alumina particulates

New aluminum matrix composites strengthened by Al2O3 particulates through stirring cast by adding NH4Al（SO4）2 to the molten aluminum have been fabricated. TEM observation shows that in-situ Al2O3 particulates are generally spherical and they are uniformly distributed in the Al matrix. Dry sliding wear test results show that the volume loss of the unreinforced Al matrix is about three times that of the Al2O3 reinforced metal matrix composite （MMC） and the volume loss of the MMC fabricated by adding Al2O3 is larger than that of the MMC by adding NH4Al（SO4）2. Lubricating sliding wear test results show that the volume loss of the MMCs increases more slowly than that of the matrix with the increasing of the load.     

Design,preparation, and structure of particle preforms for Si3N4（p）/Si3N4 radome composites prepared using chemical vapor infiltration process

A particle preform was designed and prepared by conglomerating and cold-pressed process, which was condensed by chemical vapor infiltration （CVI） process to fabricate silicon nitride particles reinforced silicon nitride composites. The conglomerations are of almost sphericity after conglomerated. There are large pores among the conglomerations and small pores within themselves in the preform according to the design and the test of pore size distribution. The pore size of the preform is characterized by a double-peak distribution. The pore size distribution is influenced by conglomeration size. Large pores among the conglomerations still exist after infiltrated Si3N4 matrix. The conglomerations, however, are very compact. The CVI Si3N4 looks like cauliflowershaped structure. 2008 University of Science and Technology Beijing. All rights reserved.     

Preparation of 2024/3003 gradient materials by semi-continuous casting using double-stream-pouring technique

1　ＩＮＴＲＯＤＵＣＴＩＯＮＧｒａｄｉｅｎｔｍａｔｅｒｉａｌｓｃｏｍｂｉｎｅｔｈｅａｄｖａｎｔａｇｅｓｏｆｉｎｄｉｖｉｄｕａｌｒａｗｍａｔｅｒｉａｌｓａｎｄｈａｖｅｌａｒｇｅｄｅｇｒｅｅｏｆｆｒｅｅｄｏｍｉｎｄｅｓｉｇｎ .Ｓｏｔｈｅｙａｒｅｖｉｅｗｅｄａｓａｎｅｗｇｅｎｅｒａｔｉｏｎｏｆｃｏｍｐｏｓｉｔｅｍａｔｅｒｉａｌｓａｎｄｈａｖｅｄｒａｗｎｇｒｅａｔａｔｔｅｎｔｉｏｎ .Ｍａｎｙｎｅｗｐｒｅｐａｒａｔｉｏｎｔｅｃｈｎｏｌｏｇｉｅｓｗｅｒｅｄｅｖｅｌｏｐｅｄ[1 7] .Ｔｈｅｐｒｅｐａｒａｔｉｏｎｔ…     

Microstructure of aluminum/copper clad composite fabricated by casting-cold extrusion forming

An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significa...     

熔融渗入法制备牙科用氧化铝基玻璃复合材料

采用熔融渗入法制备了牙科用氧化铝基玻璃复合材料，为了提高材料的强度和韧性，在氧化铝预制体中加入了一定量的氧化锆。借助SEM和XRD对材料的微观结构和晶相组成进行了研究。研究结果表明：氧化铝基体经玻璃渗透以后抗折强度等性能明显改善，而且材料的化学性能稳定，色泽逼真，是一种较理想的牙科用材料；4Y—TZP的引入量为15wt％时，复合材料的抗折强度可达到182MPa。     

Process parameters of manufacturing single crystal copper by heated mold continuous casting

1Introduction Withthedevelopmentofthetechnologyinelectron ics,telecommunicationsandAV,itisnecessarytotrans ferallkindsofsignalswithahighfidelity(Hi Fi)anda super definitioninordertomeettheincreasingrequire mentsoftelecommunicationsandmodernsciencetechnol …