冷喷涂SiC/Al纳米复合涂层的组织结构与性能

为制备基体相晶粒细小、增强相均匀分布的SiC/Al纳米复合涂层,以Al、SiC为原料,采用高能球磨法获得SiC颗粒弥散分布的纳米晶Al基复合材料粉末,利用冷喷涂技术低温成型制备了SiC/Al纳米复合涂层,分析了SiC含量对复合涂层相结构、晶粒尺寸、微观结构、硬度及磨损性能的影响规律。结果表明：冷喷涂可实现球磨纳米晶复合粉末结构的原位移植,所制备SiC/Al纳米复合涂层组织致密,微米及亚微米级SiC弥散分布在纳米晶Al（约80 nm）基体之上;SiC颗粒对Al基体有明显强化作用,冷喷涂SiC/Al纳米复合涂层的硬度随SiC体积分数的增加而显著增加,50% SiC/Al纳米复合涂层的硬度高达515 HV_0.3,约为Al块材的13倍;冷喷涂SiC/Al纳米复合涂层的耐磨损性能随着SiC含量增加而显著提高,涂层磨损失效机制为磨粒对基体的切削犁沟变形。     

Al-SiC powder preparation for electronic packaging aluminum composites by plasma spray processing

Powders of pure aluminum (Al) with 55 and 75 vol.% SiC particles were ball milled in a conventional rotating ball mill with stainless steel and ZrO₂ balls for 1–10 h. The morphology and microstructure of the milled powders have been observed and analyzed by scanning electron microscopy (SEM) and energy dispersive x-ray (EDX). The milled powders were plasma sprayed onto a graphite substrate to obtain Al matrix composites with high SiC volume fraction. SiC particles in the milled powders existed in two forms; i.e., the combination of Al into composite powder and individual. Plastic Al particles were broken during ball milling, and fine Al particles can be coated onto the surface of SiC particles. Iron contamination in the milled powders occurred when stainless steel balls were used. The iron level can be effectively controlled by using ZrO₂ ball media. The milling efficiency by ZrO₂ balls is inferior to that by stainless steel balls. Longer milling time was required with ZrO₂ balls to achieve the same effect as obtained with stainless steel balls. SiC particles in the sprayed composites from the milled powders exhibited a reasonably uniform distribution and high volume fraction.     

Mechanical Properties of Al/BN Nanocomposites Fabricated by Planetary Ball Milling and Conventional Hot Extrusion

In this study, Al matrix nanocomposites containing 1, 2 and 4 wt% nano-boron nitride were fabricated by mechanical milling and hot extrusion. The mechanical properties of all extruded samples were evaluated. Also, the morphology and microstructure of the milled composite powders were characterized using two types of electron microscope. The results showed that a high fraction of the boron nitride nanoparticles dissolved and formed a solid solution in Al matrix during the milling process. Through the process of solid solution formation, the work hardening rate of the composite powders increased. This led to a morphological change in the composite powders and resulted in equiaxed shape. The powder particle size also decreased after the milling process. By increasing boron nitride content within a range of 0–4 wt% in the hot extruded samples, tensile stress increased from 212 to 333 MPa. The hardness of the nanocomposite samples including 1, 2 and 4 wt% boron nitride improved approximately 55, 70 and 90% in comparison with pure Al,respectively.     

Preparation technique of SiCp reinforced Al matrix composite

The advancement of modern technology in the areas of aerospace and automotive industries has generated demand for new engineering materials, leading to a rapid development of metal matrix composites (MMCs) [1]. These composites can be tailored to have outstanding mechanical and physical properties such as high specific strength and stiffness, increased wear resistance, enhanced high-temperature performance and better thermal, mechanical fatigue and creep resistance than those of monolithic mat…     

硬磁／软磁纳米复合颗粒的声化学制备

利用超声波使金属有机化合物Fe（CO）5在低温和惰性气氛环境中分解生成纳米尺寸Fe颗粒，并使其包覆在硬磁颗粒表面，制备出Sm-Fe-N，Fe和Nd-Fe-B／Fe纳米复合粉末。透射电子显微镜及能谱分析表明，Fe（CO）5声化学分解得到了纯净的Fe颗粒，其尺寸约为5nm；运用场发射扫描电子显微镜对包覆产物的显微形貌进行了观察，结果显示Fe在两种永磁颗粒表面可以实现均匀包覆，且包覆的Fe含量可调；能谱分析表明，超声化学包覆过程中未生成其他副产物。此外，讨论了纳米Fe颗粒的包覆制备工艺条件和机制。     

B_4C/BN纳米复合粉末的制备与显微结构的研究

利用H38O3和CO(NH2)2在高温下发生化学反应生成纳米BN,并且形成纳米BN包覆B4C颗粒的B4C/BN纳米复合粉末.利用X射线衍射(XRD),透射电镜(TEM)和选区电子衍射(SAED)对所制备的复合粉末的物相组成和显微结构进行了研究,并且对热压烧结块材的物相组成进行了研究.物相组成和显微结构的研究结果表明,在850℃氮气气氛下热处理6 h所得到的复合粉末主要是非晶态纳米BN涂层包覆在B4C颗粒表面所形成的B4C/BN纳米复合粉末,而且非晶态BN包覆层的厚度为300～500 nm.此非晶态BN相在1850℃,30 MPa,1 h的热压烧结工艺条件下完全转变成晶态的h-BN相.     

SiC颗粒尺寸对镍基复合镀层耐磨性和耐蚀性的影响

在正交实验基础上,对比研究微米SiC(平均粒径1.5 μm)和纳米SiC(平均粒径20 nm)增强复合镍基镀层的摩擦磨损行为和耐腐蚀性能.通过TEM、SEM、EDX和XRD等手段研究颗粒分散状态以及复合镀层的表面和截面形貌、成分及相结构.采用球-盘滑动摩擦磨损试验机研究复合镀层的耐磨性.电化学阻抗谱测量在3.5%的NaCl水溶液中进行.结果表明:微米级颗粒增强复合镀层可以获得更高的表面硬度,两种增强复合镀层具有相似的摩擦磨损行为.电化学阻抗谱分析表明:SiC颗粒的加入可以提高镀层的耐腐蚀性,且纳米颗粒复合镀层具有更好的耐蚀性.     

Cr,Al颗粒尺寸对Ni-Cr-Al复合镀层氧化行为的影响

分别用纳米颗粒Cr(平均尺寸62 nm),Al(平均尺寸85 nm)和微米颗粒Cr和Al(平均尺寸3μm)复合电沉积制备Ni-11Cr-3Al纳米复合镀层(ENC)和Ni-11Cr-7Al微米复合镀层(EMC).纳米颗粒的复合使ENC Ni-11Cr-3Al比EMC Ni-11Cr-7Al的颗粒分布更加均匀,颗粒间距减...     

Microstructure characteristics of SiC particle-reinforced aluminum matrix composites by plasma spraying

Aluminum with 55 and 75 vol.% SiC powders were ball milled as plasma spray feedstock. The feedstock was deposited onto a graphite substrate to form a freestanding composite by air plasma spraying. The microstructure characteristics of the sprayed composite were investigated by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The SiC volume fraction and porosity in the sprayed composites depend on plasma spray conditions. The silicon phase was formed in the sprayed composites in some plasma spray conditions, and its amount was related to the input of electrical power into the plasma spray. The mechanism of silicon formation was studied. In the sprayed composites, no reaction products could be observed in the Al/SiC interface. Impurity materials from ball media, stainless steel, and ZrO₂ reacted with aluminum and silicon to form complex compounds during plasma spray deposition.     

球磨工艺对机械合金化合成Ti3SiC2的影响

以3Ti/Si/2C/0.2Al单质混合粉体为原料,采用机械合金化法制备Ti3SiC2材料.研究球磨工艺(球磨时间、球料比和球径大小、过程控制剂)对机械合金化合成Ti3SiC2影响.结果表明,机械合金化(球料比10:1,球径10 mm)单质混合粉体7 h后,原料粉体发生化学反应,生成了TiC和Ti3SiC2粉体和块体产物.球料比和球径大小对反应合成Ti3SiC2影响并不显著,但明显影响反应的孕育期.适当增大球径和球料比可明显缩短反应的孕育期,采用较大的磨球或过高的球料比会降低球磨效率,延长孕育期;添加过程控制剂(乙醇),不但会延长反应的孕育期,而且抑制反应合成Ti3SiC2.     

Consolidation of Al2O3/Al Nanocomposite Powder by Cold Spray

While the improvement in mechanical properties of nanocomposites makes them attractive materials for structural applications, their processing still presents significant challenges. In this article, cold spray was used to consolidate milled Al and Al₂O₃/Al nanocomposite powders as well as the initial unmilled and unreinforced Al powder. The microstructure and nanohardness of the feedstock powders as well as those of the resulting coatings were compared. The results show that the large increase in hardness of the Al powder after mechanical milling is preserved after cold spraying. Good quality coating with low porosity is obtained from milled Al. However, the addition of Al₂O₃ to the Al powder during milling decreases the powder and coating nanohardness. This lower hardness is attributed to non-optimized milling parameters leading to cracked particles with insufficient Al₂O₃ embedding in Al. The coating produced from the milled Al₂O₃/Al mixture also showed lower particle cohesion and higher amount of porosity.     

生坯制备参数对反应烧结碳化硅显微组织与性能的影响

研究了反应烧结碳化硅陶瓷的显微组织和性能与生坯碳含量、成型压力以及碳粉粒度的关系,结果表明：生坯成型压力与生坯含碳量存在最佳匹配、原则,陶瓷性能随之降低,对于一定粒度的碳化硅粉而言,加入到生坯中碳粉粒度应小于一定尺寸,否则,陶瓷的断裂强度和密度将随碳粉应变的增大而降低。     

NiCo-SiC纳米复合镀层的耐蚀性和摩擦学性能

用电沉积方法在不锈钢表面制备了NiCo-SiC纳米复合镀层,考察了不同纳米颗粒含量镀液的阴极极化曲线,测定了纳米复合镀层的晶体结构,分析了镀层的表面形貌和磨损形貌.结果表明:加入纳米SiC颗粒后,金属的还原电位发生负移,镀层表面晶粒形貌由针状变为颗粒状;NiCo-SiC纳米复合镀层比NiCo合金镀层具有更好的抗腐蚀性和摩擦学性能;磨损表面形貌显微分析表明合金镀层的磨损机制主要是粘着磨损,表面发生了严重的擦伤和塑性变形,而纳米复合镀层的磨损机制是典型的磨粒磨损.     

液氮球磨制备纳米SiCp/Al基复合材料的研究

利用液氮球磨技术制备了纳米SiC颗粒增强铝基复合材料粉末,对该纳米粉末进行真空热压和热挤压,获得纳米铝基复合材料块体.采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)研究了纳米SiC粉和Al-Zn-Mg-Cu粉在液氮球磨过程中形貌、组织和相组成等.结果表明,液氮球磨可以使复合材料粉末达到纳米级,且纳米SiC可均匀地分布于铝合金中.     

纳米SiC和添加剂ZrO2对Al2O3基纳米复合陶瓷显微组织和性能的影响

采用极性分散剂,在微米Al2O3基体中加入微米ZrO2和纳米SiC颗粒,用真空热压法制备出了Al2O3/SiC纳米复合陶瓷,并研究了微米ZrO2和纳米SiC的添加对Al2O3/SiC纳米复合陶瓷显微组织及其性能的影响.结果表明:与纯Al2O3比较,适量微米ZrO2和纳米SiC颗粒的加入阻碍了Al2O3晶粒的长大,使复合陶瓷的显微组织非常细小,纳米复合陶瓷烧结后的力学性能大大提高.     

SiCp/AZ31镁基纳米复合材料的高能超声制备及性能

文章采用自行设计的高能超声装置制备SiCp/AZ31镁基纳米复合材料,并对制备的复合材料进行显微组织观察和力学性能测试。实验结果表明,高能超声波能使纳米SiCp在镁合金熔体中均匀分散,复合材料抗拉强度和屈服强度都比基体有较大提高,并能保持较高的延伸率。另外,对高能超声波制备金属基复合材料的分散机理,以及SiCp增强镁基纳米复合材料的增强机制,进行了初步探讨。     

Microstructural and mechanical properties of Al-Mg/Al2O3 nanocomposite prepared by mechanical alloying

The effect of milling time on the microstructure and mechanical properties of Al and Al-10 wt.% Mg matrix nanocomposites reinforced with 5 wt.% Al₂O₃ during mechanical alloying was investigated. Steady-state situation was occurred in Al-10Mg/5Al₂O₃ nanocomposite after 20 h, due to solution of Mg into Al matrix, while the situation was not observed in Al/5Al₂O₃ nanocomposite at the same time. For the binary Al-Mg matrix, after 10 h, the predominant phase was an Al-Mg solid solution with an average crystallite size 34 nm. Up to 10 h, the lattice strain increased to about 0.4 and 0.66% for Al and Al-Mg matrix, respectively. The increasing of lattice parameter due to dissolution of Mg atom into Al lattice during milling was significant. By milling for 10 h the dramatic increase in microhardness (155 HV) for Al-Mg matrix nanocomposite was caused by grain refinement and solid solution formation. From 10 to 20 h, slower rate of increasing in microhardness may be attributed to the completion of alloying process, and dynamic and static recovery of powders.     

Al2O3／SiC纳米陶瓷复合材料的强化机理

采用一次粒径分别为１０ｎｍ和１５ｎｍ的α－Ａｌ２Ｏ３和ＳｉＣ超细粉体,制备了Ａｌ２Ｏ３／ＳｉＣ纳米陶瓷复合材料,并研究了其强化机理,提出了内晶颗粒残余应力强化模型。该模型很好地解释了Ａｌ２Ｏ３／ＳｉＣ纳米复合材料的强度和断裂方式随ＳｉＣ颗粒含量的变化规律。     

机械诱发自蔓延反应合成Ti3SiC2的机理研究

机械合金化3Ti/Si/2C粉体,会诱发自蔓延反应,产生组成相为TiC、Ti3SiC2、TiSi2和Ti5Si3的粉体与块体产物.获得的粉体和块体产物中Ti3SiC2含量分别约为17.6%和58.2%(质量分数,下同).本研究提出了一个机械诱发自蔓延反应合成Ti3SiC2的反应机制,即Ti3SiC2是从固相TiC与Ti-Si液相中形核并长大.最后讨论了机械诱发自蔓延反应与自蔓延高温烧结对合成产物中Ti3SiC2含量及显微形貌的影响.     

Synthesis of sub-micron nickel particles coated onto aluminum powders via a modified polyol process

Aluminum is commonly used as a fuel additive for propellants. The main limitations to its use lie in comparatively slow ignition and oxidation/combustion kinetics. Combustion performance of aluminized propellants can be improved through the use of Ni-coated Al particles. Sub-micron to nano-sized particles, with their increased reactivity, also improve combustion performance. Hence, in these contexts, fine Ni particles coated onto commercially available micron-sized Al powders using a modified polyol process were synthesized and evaluated. Ni-coated Al powders of various compositions produced by this method showed significant improvement in oxidation kinetics compared to untreated Al powders. The onset oxidation temperatures for the Ni-coated Al powders were found to be significantly reduced compared to pure untreated Al.