SiCp/ZA27复合材料的界面结构及耐磨性研究

通过扫描电镜和高分辩透射电镜观察，经选区电子衍射和微区化学成分分析，研究了SiCp／ZA27复合材料的界面结构及耐磨性。结果表明，SiC颗粒均匀地分布于ZA27合金中，界面结合良好，SiCp颗粒周边存在着大量的CuZn4化合物。CuZn4依附于SiC颗粒形核，沿SiC晶面长大速率大于垂直于SiC晶面的长大速率。SiC颗粒显著地提高了ZA27合金的耐磨性。当SiC颗粒含量达30％时，耐磨性提高了126．5倍。     

SiC颗粒增强LD2基复合材料界面反应产物研究

本文利用金相显微镜、透射电镜及能谱仪研究了SiC颗粒增强LD_2基复合材料的界面微观结构。分析观察结果表明,SiC颗粒与α-Al固溶体发生了界面反应,反应产物为Al_4C_3与Mg_2Si。Al_4C_3呈棒状,晶内存在孪晶亚结构,孪晶面为(0003),棒的长轴方向即晶体生长方向为[1010].SiC颗粒间距过小及与液态金属接触时间过长会导致反应层厚度增加,因此适当降低SiC颗粒体积含量,避免SiC颗粒与液态金属接触时间过长,可以进一步改善材料的力学性能。     

SiC颗粒尺寸对喷射沉积铝硅复合材料高温疲劳性能的影响

采用喷射沉积法制备SiCp/Al-7Si复合材料,研究SiC颗粒尺寸对复合材料低周疲劳性能的影响.结果表明:SiC颗粒尺寸对复合材料疲劳性能的影响显著.在相同体积分数下,小尺寸SiC颗粒复合材料的间距小、承载能力强,表现出较高的疲劳寿命,疲劳裂纹主要在SiC颗粒与基体脱粘处以及小尺寸颗粒团聚处形核并扩展.而在SiC颗粒尺寸为20 μm的SiCp/Al-7Si复合材料中,大尺寸的SiC颗粒更易出现自身的断裂,使得其疲劳性能降低.温度的升高会使复合材料基体发生软化,承载能力下降,高温下大尺寸SiC颗粒更易发生与基体的脱粘,加速疲劳裂纹的形核、孔洞的长大,造成复合材料疲劳性能的下降.     

SiC(w)-ZrO2改性MoSi2复相陶瓷的组织与性能

通过热压烧结制备SiC(W)-ZrO2-MoSi2复相陶瓷,利用X射线衍射仪、图像分析仪、透射电镜对复相陶瓷试样组织结构进行了研究,探讨了SiC(W)-ZrO2协同作用对MoSi2陶瓷性能的影响.结果表明:纳米ZrO2颗粒的加入对材料的细化作用较SiC晶须明显,复相协同作用细化效果更好.SiC(W)-ZrO2协同作用的综合机制有利于提高复相陶瓷的抗弯强度和断裂韧性,ZrO2量的增加对提高复相陶瓷断裂韧性的作用更明显;ZrO2粒子钉扎位错,导致可动位错绕过,强化材料基体.弥散分布的SiC晶须阻碍位错运动,使位错缠结、交割,阻碍晶界迁移;粒子周围出现孪晶以及SiC晶须引起的层错,阻碍其晶粒长大.     

原位合成Ti3SiC2/SiC复合材料及其显微组织的观察

利用Si和TiC原位反应合成了Ti3SiC2/SiC复合材料.研究了不同烧结工艺参数和原料配比对形成复合材料的影响.利用X-射线衍射分析了材料的物相组成.所合成的材料中除Ti3SiC2和SiC外,还有TiC存在.利用扫描电镜和透射电镜观察了材料的微观组织,发现生成的SiC颗粒呈棒状和等轴状分布于Ti3SiC2基体中.在Ti3SiC2晶粒内部存在大量的位错和层错.     

纳米SiC颗粒强化7075铝合金在NaCl溶液中的电化学腐蚀行为

研究了纳米SiC颗粒强化7075铝合金(SiC_p/7075A1)经T6处理后在3.5%NaCl中性水溶液中的腐蚀特性及腐蚀机理.结果表明,适量纳米SiC颗粒的加入,可提高AA7075-T6的自腐蚀电位和击穿电位,降低腐蚀速率,增强其耐蚀性.SEM观察表明,SiC_p/7075Al-T6的腐蚀以点蚀为主,主要发生在晶界及近晶界区域,没有大的点蚀坑,而未经强化的AA7075-T6则呈现出严重的点蚀和晶间腐蚀的特征,这与EIS特征相符,浸泡实验也得到了同样的结果.TEM观察证实SiC颗粒在晶界的存在分割了η相;阻断了晶界阳极性的η相与其边缘合金组成的腐蚀电偶形成的活性通道;阻碍了蚀孔的长大,提高了腐蚀抗力.     

常规铸造工艺条件下SiC颗粒增强Al-Si系铸造合金的界面反应

采用透射电镜，研究了SiC颗粒增强Al-Si系铸造铝合金复合材料在常规铸造工艺条件下的界面反应。试验结果表明：当基体合金含硅量为5％以上时，能抑制生成Al4C3的有害界面化学反应，SiC界面基本上是单一的SiC／Al及SiC／Si界面，且部分界面上有MgAl2O4颗粒相形成。此外，对不同文献所述的抑制有害相Al4C3产生所需的临界Si含量的差异进行了分析。     

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.     

SiC纳米颗粒增强A356铸造合金的表征(英文)

通过搅拌铸造制备SiC纳米颗粒增强A356铝合金复合材料,并研究其显微组织和力学性能。密度测量发现试样的孔隙度较低,且孔隙度随SiC颗粒体积分数的增加而增加。通过光学显微镜和透射电镜观察材料的显微组织,发现弥散的颗粒分布均匀。材料的拉伸强度和弹性模量随加入纳米SiC颗粒的增加而提高,而延展性有所降低。当SiC纳米颗粒的加入量为3.5%时,复合材料的屈服强度和极限抗拉强度达到最高。断口分析表明,拉伸断裂试样为相对韧性断裂。     

SiC颗粒表面Mo涂层的制备与分析

采用磁控溅射法在碳化硅(SiC)颗粒表面成功制备了金属钼(Mo)涂层,分析了Mo涂层的成分和形貌;为改善初始涂层成分和形貌,对镀Mo改性SiC复合粉体进行了不同工艺的结晶化热处理,重点研究了热处理对SiC颗粒表面Mo涂层形貌和成分的影响。结果表明,磁控溅射法能够在SiC颗粒表面沉积Mo涂层,随磁控溅射时间的延长,SiC颗粒表面Mo涂层的粗糙度增大,但磁控溅射后SiC颗粒表面Mo涂层为非晶态。热处理能够有效改善SiC颗粒表面Mo涂层的成分、形貌及结晶状态,在600~1200℃之间结晶化热处理过程中,随热处理温度升高,SiC颗粒表面Mo涂层形貌主要经历了以下4个阶段变化:Mo涂层初步致密化—Mo的结晶致密化—Mo涂层的聚集长大—Mo与SiC之间化学反应;相应的Mo原子的存在状态也经历了如下变化:非晶态Mo原子—晶态Mo原子—Mo_2C和MoSi_2。其中800~900℃之间为最佳热处理温度,此时Mo涂层致密均匀包覆完整。SiC表面连续均匀致密的Mo涂层,有利于改善SiC颗粒增强金属基复合材料中基体与增强体之间的界面结合并控制不利界面反应,有利于复合材料综合性能的提高,必将扩大SiC颗粒作为增强体的应用范围。     

Process for dense 2D SiC fiber-SiC matrix composites

A new process using SiC fiber fabrics and SiC tapes to produce dense 2D SiC fiber-SiC (SiC/SiC) composites is demonstrated. The strategy for fabricating the SiC/SiC composites involves: (i) alternately stacking the SiC fiber fabrics and SiC tapes at room temperature, (ii) pyrolyzing of the stacked composites, and (iii) hot-pressing the pyrolyzed composites. By controlling the hot-pressing temperature, it is possible to obtain dense 2D SiC/SiC composites with relative densities of >98%. The 2D SiC/SiC composites show no degradation of the SiC fibers and a higher mechanical strength.     

感应加热辅助原位合成Ti3SiC2连接SiC陶瓷

采用感应加热的方式引燃Ti-Si-C(摩尔比3∶1∶2)及Ti-Si-C-Al(摩尔比3∶1∶2∶0.1)体系的自蔓延燃烧反应并实现了SiC陶瓷间的连接. 通过对不同工艺参数下生成产物中Ti3SiC2相的相对含量的分析,初步优选出最佳工艺参数为50 A感应电流下加热、30 A感应电流下保温30 min以及1 MPa的连接压力,得到的SiC/TSC/SiC和SiC/TSC-Al/SiC接头平均抗剪强度分别为32.9和66.8 MPa. 微观结构和成分分析的结果表明,SiC/TSC/SiC及SiC/TSC-Al/SiC接头处均显示出良好的界面结合,无明显气孔或裂纹等缺陷.XRD的物相分析结果表明,SiC/TSC-Al/SiC接头的中间层产物中主要含有Ti3SiC2相及少量TiC和Ti-Si的化合物;而SiC/TSC/SiC接头则主要以TiC为主,这就导致了前者的平均抗剪强度超过了后者的两倍.     

Fabrication of dense 2D SiC fiber-SiC matrix composites by slurry infiltration and a stacking process

This paper reports a new process for producing dense 2D SiC fiber-SiC (SiC/SiC) composites through slurry infiltration and stacking. The processing strategy for the fabrication of the 2D SiC/SiC composites involves: (i) infiltration of the SiC fiber fabric using a SiC slurry, (ii) stacking the slurry-infiltrated SiC fiber fabric and SiC tapes alternately at room temperature, (iii) pyrolysis of the stacked composites and (iv) hot-pressing the pyrolyzed composites. It was possible to obtain dense 2D SiC/SiC composites with relative densities of >96% by controlling the hot-pressing time at 1750°C.     

Codeposition of micro- and nano-sized SiC particles in the nickel matrix composite coatings obtained by electroplating

Micro- and nano-sized SiC particles were codeposited with nickel by electrolytic plating from a nickel sulfamate bath and the effects of plating parameters such as pH of the plating bath, SiC content in the plating bath, and stirring speed on the deposition behaviors of Ni-SiC composite coating layers were studied. The result revealed that the micro-sized SiC particles are more negative than the nano-sized SiC particles in the Zeta potential. The codeposition of SiC can be increased by increasing the SiC content in the plating bath and the pH of the plating bath within the present experimental range. In case of micro-sized SiC particles, increasing stirring speed always lowered the codeposition of SiC. In case of nano-sized SiC particles, the codeposition of SiC showed a maximum at the stirring speed of 100 rpm. The nano-sized SiC particles are more difficult to codeposit than the micro-sized SiC particles and showed rougher plated surface compared with the micro-sized SiC particles, which may be attributable to the agglomeration of nano-sized SiC particles in the plating bath.     

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。     

含钇聚碳硅烷制备碳化硅纤维(英文)

将钇元素作为烧结助剂引入到聚碳硅烷(PCS)中制备含钇PCS。由含钇PCS制成SiC(OY)和SiC(Y)2种碳化硅纤维。对SiC(OY)纤维转变成SiC(Y)纤维的结构与相关特性的变化进行研究。SiC(OY)纤维的化学组成为SiC1.23O0.05Y0.005,纤维是无定型结构;SiC(Y)纤维含有大量的直径为50nm的β-SiC晶粒和少量的α-SiC晶粒,钇元素存在于SiC晶粒之间。SiC(OY)的拉伸强度为2.25GPa,断裂韧性为2.37MPa.m1/2;SiC(Y)的拉伸强度为1.61GPa,断裂韧性为1.91MPa.m1/2;SiC(Y)纤维比SiC(OY)纤维具有更好的热稳定性。     

Bulk Al/SiC nanocomposite prepared by ball milling and hot pressing method

Nano-sized Al/SiC powders were prepared by mechanical alloying method. Two sorts of SiC particle, i.e., nano-sized and popular micron-sized SiC were utilized. The particle size and microstructure of the milled powder were characterised. Effects of the particle size and agglomerate state of SiC, as well as the microstructure of Al/SiC nanocomposite were studied by SEM and TEM. The results show that nano-sized SiC particles is dispersed in aluminium uniformly after ball milled for only 2 h, whereas the similar process need about 10 h for popular micron-sized SiC particle. The bulk Al/SiC nanocomposite can be fabricated by hot pressing the nano-sized Al/SiC powders at temperature about 723 K under pressure of 100 MPa.     

Fabrication of protective-coated SiC reinforced tungsten matrix composites with reduced reaction phases by spark plasma sintering

SiC reinforced tungsten matrix composites were fabricated via the spark plasma sintering process. In order to prevent an interfacial reaction between the SiC and tungsten during sintering, TiOx coated SiC particles were synthesized by a solution-based process. TiOx layer coated SiC particles were treated in high temperature nitriding conditions or annealed in a high temperature vacuum to form TiN or TiC coated SiC particles, respectively. The TiC layers coated on SiC particles successfully prevented tungsten from reacting with SiC; hence the proposed process resulted in successful fabrication of the SiC/W composites. The mechanical properties such as compressive strength and flexural strength of the composites were measured. Additionally, the effect of SiC on the high temperature oxidative ablation of tungsten was also investigated. The addition of SiC resulted in an improved oxidative ablation resistance of the tungsten-based composites.     

Study on Photoluminescence Spectra of SiC

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Electrolytic deposition behaviors of Ni−SiC composite coatings containing submicron-sized SiC particles

Submicron-sized SiC particles (130 nm mean diameter) were codeposited with nickel by electrolytic plating in a nickel sulfamate bath to from Ni−SiC composite coatings. The effects of plating parameters, such as pH of the plating bath, SiC content in the plating bath, stirring rate, and current density on the deposition behaviors of Ni−SiC composite coatings were investigated. Results revealed that zeta potential decreased with increasing pH; the iso-electric point was measured to be }7.0 in pH. The codeposition of SiC increased with increasing pH, and the deposition rate increased with increasing SiC content in the plating bath. This may be due to the increased flux of approaching SiC particle towards the cathode due to enhanced SiC content in the plating bath. The codeposition of SiC exhibited a maximum at the stirring rate of 100 rpm. This can be explained by hydrodynamic effects and particle characteristics. The deposition rate increased with increasing current density. The codeposition of SiC increased up to a maximum of 15 A/dm² and then decreased This can be explained by electrophoretic movement of the SiC particles due to the adsorption of nickel ions and protons in the plating bath on the SiC particle surface. Submicron-sized SiC particles provided for a rough plating surface. This effect may be attributable to the strong tendency of submicron-sized SiC particles to agglomerate in the plating bath.