Validation of Numerical Modeling for the Prediction of Elastic and Failure Behavior of Diamond Powder Filled Woven Composites

A numerical investigation was carried out to examine the role of micro-sized diamond powder filler on the on-axis tensile stiffness properties of the standard modulus T300 and the high modulus YS90A woven fabric composite plates by progressive damage modeling. Finite element modeling (FEM) results for the T300 composite with and without diamond powder predicted a specific case of fiber failure in all the plies showing the characteristics of brittle failure. Static tensile tests were carried out on the YS90A composite coupons containing no diamond powder (DP) and filled with 6% and 12% volume fractions of DP. A higher content of diamond powder in the coupons led to agglomeration. This induced stress concentrations and subsequently reduced the mechanical properties. FEM was carried out considering specimens with and without an induced stress concentration geometry in the YS90A coupons filled with DP. The results of the on-axis tensile tests indicated a delamination type of failure in both cases with additional fiber fracture in the Open Hole Tensile (OHT) coupons.

Effect of heat treatment on microstructure and thermophysical properties of diamond/2024 Al composites

50%diamond particle （5μm） reinforced 2024 aluminum matrix （diamond/2024 Al） composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, and no apparent porosities or significant casting defects were observed in the composites. The diamond-Al interfaces of as-cast and annealed diamond/2024 Al composites were clean, smooth and free from interfacial reaction product. However, a large number of Al2Cu precipitates were found at diamond-Al interface after aging treatment. Moreover, needle-shaped Al2MgCu precipitates in Al matrix were observed after aging treatment. The coefficient of thermal expansion （CTE） of diamond/2024 Al composites was about 8.5×10-6 °C-1 between 20 and 100 °C, which was compatible with that with chip materials. Annealing treatment showed little effect on thermal expansion behavior, and aging treatment could further decrease the CTE of the composites. The thermal conductivity of obtained diamond/2024 Al composites was about 100 W/（m？K）, and it was slightly increased after annealing while decreased after aging treatment.

Microstructural characterization and mechanical properties of friction surfaced AA2024-Ag composites

The effects of Ag on the microstructure, mechanical properties, and electrical conductivity of AA2024 aluminum alloy coating were investigated. It was fabricated by friction surfacing as an additive manufacturing process. To carry out this investigation, Ag was added by 5.3, 10.6, and 16.0 wt.% to an AA2024 consumable rod by inserting holes in it. It was found that due to the strengthening by solid solution and the formation of precipitates and intermetallic containing Ag, the driving force for grain growth is reduced and consequently the grain size of the coating is decreased. After artificial aging heat treatment, the electrical conductivities of the coatings containing 0 and 16.0 wt.% Ag are increased by 4.15%(IACS) and decreased by 2.15%(IACS), respectively. While considering a linear relationship, it can be proposed that for a 1 wt.% Ag increase, the strength and hardness of the coating will be increased by 1.8% and 1.0%, respectively. It was established that the effect of Al6(Cu,Ag)Mg4 precipitate formation on strengthening is greater than that of Ag-rich intermetallic.

Fabrication of Sintered Diamond/Metal Composites and Evaluation of Grinding Performance for Sapphire

The fabrication of sintered diamond/metal composites bodies composed of diamond filler with the average particle size of 15 μm to 30 μm and metal binder (Ag-Cu-Ti system brazing) was attempted by powder metallurgical sintering process at 700℃ to 1000?C in vacuum atmosphere. As a result, dense bulks of sintered diamond/metal composites were obtained by this powder metallurgical sintering process. The increase of sintering temperatures from 750℃ to 950℃ and of pressure enhanced the density of sintered diamond/metal composites during the hot-pressing in vacuum. All bulks prepared at the temperatures of 750?C to 950℃ were composed of diamond phase and Ag-Cu-Ti system brazing without any other phase for sintered bulks for diamond/metal composites. Furthermore, some properties were evaluated for sintered diamond/metal composites.

AgCl/Ag复合粉体材料的制备及机理

采用超声辅助脱合金法,以Ca-Mg-Cu-Ag非晶条带为前驱体,Cu-Ag纳米多孔材料为中间产物,不同溶剂组成的盐酸溶液为反应液,制备出不同形貌的AgCl粉体材料,利用SEM、XRD等检测手段对样品的形貌、结构、成分等进行了表征分析,揭示了AgCl/Ag复合粉体材料在不同反应液中的形成过程及机理。研究表明:在超声辅助作用下,当以盐酸乙醇溶液为反应液时,改变浓盐酸溶液与乙醇溶剂的体积比后Cu-Ag纳米多孔材料可以完全溶解于该溶液中并重新析出不同形貌的AgCl粉体材料;而以盐酸水溶液为反应液时,改变盐酸水溶液与蒸馏水溶液的体积比后Cu-Ag纳米多孔材料只能直接转变为近球形的AgCl粉体材料,且不能溶解于盐酸水溶液中再重新析出。在超声与盐酸乙醇溶液的共同作用下,Cu-Ag纳米多孔材料存在一种新颖的AgCl“生成-溶解-再析出”机制,可以精准地控制再析出AgCl晶体的形貌和尺寸。

TiC-Maraging stainless steel composite:microstructure, mechanical and wear properties

Particulate TiC reinforced 17-4PH and 465 maraging stainless steel matrix composites were processed by conventional powder metallurgy （P/M）. TiC-maraging stainless steel composites with theoretical density 〉97% were produced using conventional P/M. The microstructure, and mechanical and wear properties of the composites were evaluated. The microstructure of the composites consisted of （core-rim structure） spherical and semi-spherical TiC particles depending on the wettability of the matrix with TiC particles. In TiC-maraging stainless steel composites, 465 stainless steel binder phase showed good wettability with TiC particles. Some microcracks appeared in the composites, indicating the presence of tensile stresses in the composites produced during sintering. The typical properties, hardness, and bend strength were reported for the composites. After heat treatment and aging, an increase in hardness was observed. The increase in hardness was at- tributed to the aging reaction in maraging stainless steel. The specific wear behavior of the composites strongly depends on the content of TiC particles and their interparticle spacing, and on the heat treatment of the maraging stainless steel.

Study on the diamond/ultrafine WC-Co cermets interface formed in a SPS consolidated composite

Nanocrystalline WC-Co composite powder and coated tungsten diamond by using vacuum vapor deposition were consolidated by the spark plasma sintering （SPS） process to prepare diamond-enhanced WC-Co cemented carbide composite materials. The interface microstructures between coated tungsten diamond and WC-Co cemented carbide matrix were investigated by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDXS）. The results showed that there is a transitional layer between the diamond and the matrix, in which the carbon content is 62.97wt.%, and the content of cobalt in the transitional zone is 6.19wt.%; the content of cobalt in the WC-Co cemented carbide matrix is 6.07wt.%, in which the carbon content is 15.95wt.%, and the content of cobalt on the surface of diamond is 7.30wt.%, in which the carbon content is 80.38wt.%. The transitional zone prevents the carbon atom of the diamond from spreading to the matrix, in which the carbon content does coincide with the theoretical value of the raw nanocomposite powders, and the carbon content forms a graded distribution among the matrix, transitional zone, and the surface of diamond; after the 1280℃ SPS consolidated process the diamond still maintains a very good crystal shape, the coated tungsten on the surface of the diamond improves thermal stability of the diamond and increases the bonding strength of the interface between the diamond and the matrix.

激光粉末床熔融成形金刚石增强铝基复合材料

添加质量分数3%金刚石颗粒并利用激光粉末床熔融技术制备6061铝基复合材料。采用光学显微镜、扫描电子显微镜、X射线衍射仪、电子密度计、电子式万能试验机对3%金刚石/6061铝基复合材料的微观组织、相对密度和拉伸性能进行了表征与分析。结果表明:金刚石与Al基体反应生成了针状Al4C3相,并沉积在α-Al基体上,导致晶界位错密度增加,强度提高,抗失效能力增强。金刚石的添加促使6061铝基体中热裂纹消失,但存在孔洞缺陷。较低的扫描速度增加了激光光斑与被加工材料接触的时间,导致金刚石颗粒部分石墨化,铝基体部分蒸发,进而形成内部缺陷,降低了复合材料的相对密度(97%)。金刚石的加入显著提高了激光粉末床熔融技术成形金刚石/6061铝基复合材料的抗拉强度,当激光功率为350 W、扫描速度为800 mm·s-1时,复合材料的极限抗拉强度达到最大值244.2 MPa,屈服强度211.6 MPa,伸长率2.1%。

纳米Ag-Al_2O_3复合粉末的制备

用甲醛-银氨溶液,在超声波辐照下对10～20nm的Al2O3粉末进行化学镀银,制备出了纳米Ag-Al2O3复合粉末,并探讨了镀液组成及其工艺条件对纳米Al2O3粉末化学镀银的影响.结果表明,改变镀液中氨水的含量和pH值可以控制镀液的稳定性和反应诱导期的长短;增重测定和X射线衍射分析结果表明,调整甲醛的用量和装载量的大小可以得到重量百分比为11%～74%银的纳米Ag-Al2O3复合粉末.TEM观察的结果表明,通过该工艺所得到的Ag-Al2O3复合粉末具有很好的均匀性.

Ag-Cu-Ti活性钎料真空钎焊金刚石/Cu复合材料和金刚石膜

采用Ag-Cu-Ti活性钎料钎焊金刚石/Cu复合材料和金刚石膜,实现其高强度连接。用SEM对接头的微观组织进行观察分析,用无损探伤检测钎焊质量,用拉伸试验测定接头的力学性能,用热循环试验检验其可靠性。结果表明:焊料与金刚石膜连接处有一层均匀连续的富Ti相,大大改善了焊料与金刚石膜的润湿性;与金刚石膜粗糙面相比,采用金刚石膜光滑面进行钎焊,焊接接头的质量较高,焊缝内存留的夹孔、气泡等缺陷较少,热导率较高;钎焊接头的抗拉强度>23.12MPa,能够承受50个周期的冷热循环,满足实际应用的要求。

金刚石/铜复合材料与氧化铝陶瓷的Ag-Cu-Ti活性钎焊(英文)

金刚石/铜复合材料具有低膨胀系数和高热导率等优异性能,使其成为一种理想的电子封装材料。采用97%(72Ag-28Cu)-3%Ti活性钎料对金刚石/铜复合材料和氧化铝陶瓷进行钎焊。发现活性钎料在氧化铝陶瓷和金刚石薄膜表面均具有良好的润湿性,在两者表面的平衡润湿角均小于5°。讨论了主要钎焊条件(如钎焊温度和保温时间等)对接头性能的影响。发现钎焊过程中Ti元素聚集在金刚石颗粒的表面形成TiC化合物,且TiC化合物的形貌与钎焊接头的剪切强度具有紧密联系。推测合适的TiC化合物层厚度可改善钎焊接头的剪切强度,而颗粒状的TiC化合物及过厚的TiC化合物层却会损害钎焊接头的性能。获得的最大剪切强度为117MPa。

溶胶凝胶法制备超细W-Ag复合粉末

采用溶胶-凝胶法制备了W-Ag复合氧化物粉末,再经过氢还原获得超细W-20%Ag（质量分数）复合粉末。采用热重分析（TG）、X射线衍射仪（XRD）和扫描电镜（SEM）对干凝胶的分解过程,还原前后粉末的物相组成、粒度和形貌进行分析。结果表明：干凝胶在煅烧和还原过程发生一系列的分解和化合反应,随着温度的升高,粉末的相组成、颗粒尺寸和形貌发生明显变化;SEM结果分析表明,还原后W-Ag复合粉末呈球形或近球形,颗粒直径在200~400 nm。

Ag包覆Fe_3O_4复合粉体的制备及其性能研究

用化学镀法,甲醛为还原剂,制备Fe3O4/Ag包覆复合粉体。用XRD、SEM和EDX对粉体进行表征。用重法测定粉体的抗氧化性能,并研究了AgNO3用量对Fe3O4/Ag包覆复合粉体的导电性能的影响。结果表明,用该法制备的Fe3O4/Ag包覆复合粉体能够实现表面银层包覆完整;Fe3O4粉镀银后的抗氧化性能得到一定程度的提高;AgNO3用量越多,Fe3O4/Ag包覆复合粉体的导电性能越好。

Ag-Cu-Ti钎焊金刚石/铜复合材料的组织和性能

采用97(72Ag-28Cu)-3Ti活性钎料钎焊了Diamond/Cu复合材料和Al2O3陶瓷,研究了主要钎焊条件如钎焊温度和保温时间对接头强度的影响。结果表明,钎焊过程中Ti元素易聚集在金刚石颗粒周围并形成TiC化合物层。TiC化合物的形貌与Diamond/Cu钎焊接头剪切强度有密切关系,金刚石表面生长适当厚度的TiC化合物层能增强钎焊接头的剪切强度,但如果TiC为颗粒状或TiC化合物层生长过厚,将削弱钎焊接头的剪切强度。钎焊接头的最大剪切强度可达117 MPa。

SBS/橡胶粉复合改性混合植物沥青的制备及其性能研究

针对特定来源的植物沥青,将其与克拉玛依90号沥青(K-90)共混制备混合植物沥青后进行聚苯乙烯-丁二烯-苯乙烯(SBS)/橡胶粉复合改性,通过研究复合改性顺序及改性剂掺量对复合改性植物沥青路用性能的影响,从而确定混合植物沥青复合改性工艺。并对制备的SBS/废橡胶粉复合改性混合植物沥青模拟了短期热氧老化和紫外老化试验。通过比较老化前后复合改性混合植物沥青的物理性能的变化,以及利用剪切流变仪评价复合改性植物沥青的流变特性。结果表明:SBS掺入量为2.5%,橡胶粉掺入量为15%时,先进行SBS改性后进行橡胶粉改性制备的复合改性混合植物沥青的常规路用性能较优。经过SBS/废橡胶粉复合改性的混合植物沥青软化点增量减小,残留针入度比和延度保留率上升,表明SBS/废橡胶粉复合改性可明显提高混合植物沥青的抗紫外老化性能。SBS/废橡胶粉复合改性可使混合植物沥青复数模量和车辙因子增加,相位角下降,说明SBS/废橡胶粉复合改性可提高混合植物沥青的抗车辙性能。

电子元件用Pd-Ag粉末工业化生产工艺与设备

介绍了电子元件用高纯超细球形钯银复合粉的工业生产工艺、形貌控制方法及其生产设备特点 ,探讨了影响钯银复合粉质量的各个因素。用本工艺与设备生产的钯银复合粉纯度高 ,颗粒呈球形 ,粒径在 0 1 μm～ 0 8μm ;粒径分布窄 ,0 2 μm～ 0 6μm的颗粒占95 %以上 ;在粒径 0 4μm附近 ,颗粒出现的相对百分率频率最大 ;

咖啡壳粉对木塑复合材料耐候性能的影响

用咖啡壳粉(CHP)代替木粉,以增强高密度聚乙烯(HDPE)的抗老化性能。以两步成型法熔融共混制备了木塑复合材料(WPCs),经过氙灯老化2000h后,测试其耐候性能。采用红外光谱(FTIR)、X射线光电子能谱(XPS)、表面颜色、机械性能、热稳定性、微观形貌(SEM)来测试WPCs的抗老化性能。结果表明,在老化2000 h后,CHP高混杂样品(HCHP/HDPE)的降解速率加快,使其更容易褪色和开裂;而CHP低混杂样品(LCHP/HDPE)的羰基指数、O/C比增幅最小(分别为136.6%、66.23%),物理性能降幅不明显,故CHP低混杂填料,可以提高桉木纤维/高密度聚乙烯(WF/HDPE)木塑复合材料的耐候性能。

Two-stage aging treatment to accelerate aging kinetics without impairing strength in B_4C/7A04Al composite

Aging treatments are the key process to obtain satisfactory strength for 7xxxAl alloys and their composites. However, traditional single-stage(SS) aging is time-consuming to reach a peak strength condition. In this study, an efficient 120℃ + 160℃ two-stage(TS) aging treatment was proposed on a B_4C/7A04Al composite fabricated via powder metallurgy(PM) technology, which could acquire similar peak-aging strength but only took about 15% of the time compared to traditional 120℃ SS aging. The evolution of precipitation during the TS aging was investigated, as well as those of the 7A04Al alloys for comparison. In the second stage aging process, the higher aging temperature accelerated the nucleation of η′ phases inside the grains and thus increased the density of precipitates. Moreover, the short aging time limited the coarsening of precipitates and the broadening of precipitatefree zones. The above factors were beneficial for quickly obtaining satisfactory precipitation strengthening effects. The B_4C/7A04Al composite exhibited slower aging kinetics than the 7A04Al alloy in the TS aging. Mg elements consumption by the chemical reaction between B impurities introduced by B_4C particles and the Al matrix was considered to potentially retard the aging kinetics of the B_4C/7A04Al composite. Nevertheless, the precipitation sequence was not affected.

钨粉粒径对金刚石扩散镀钨影响的研究

金刚石镀钨能够改善铜与金刚石的润湿性,有助于合成金刚石/铜复合材料。采用扩散烧结法对金刚石表面进行处理,研究钨粉粒径对镀层的影响。并对试验机理及规模化生产的可行性进行了论述。试验结果表明:钨粉粒径过小或过大时均镀覆失败,其最佳镀覆粒径为金刚石粒径的1/3~2/3;金刚石烧结量对镀层影响关系很小,真空扩散镀钨烧结法适用于工业批量生产。

Ag-Fe_3O_4复合粉末的制备研究

探讨了Ag-Fe3O4磁性导电复合粉末的制备方法及工艺条件。研究表明，采用超声波振荡分散，在镀液pH=10～12，反应时间≥60min，适当的Fe3O4用量下可以制备出粉末表面Ag：Fe摩尔比为55．17：37．84、具备Ag—Fe3O4壳-核结构且导电性良好的磁粉材料。此外，还借助扫描电镜、EDS能谱分析仪及电学测量等方法对粉体材料的表面形貌、化学组成和导电性进行了分析和评估。