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1.
Copper–matrix composites were made by powder metallurgy (PM). The reinforcements were molybdenum particles, silicon carbide
whiskers and titanium diboride platelets. The coated filler method, which involves a reinforcement coated with the matrix
metal, was used. In contrast, conventional PM uses the admixture method, which involves a mixture of matrix powder and reinforcement.
For all the composite systems, the coated filler method was found to be superior to the admixture method in providing composites
with lower porosity, greater hardness, higher compressive yield strength, lower coefficient of thermal expansion (CTE), higher
thermal conductivity and lower electrical resistivity, though the degree of superiority was greater for high than low reinforcement
contents. In the coated filler method, the coating on the reinforcement separated reinforcement units from one another and
provided a cleaner interface and stronger bond between reinforcement and matrix than the admixture method could provide. The
highest reinforcement content attained in dense composites (<5% porosity) made by the coated filler method was 70 vol% Mo,
60 vol% TiB2 and 54 vol% SiC. The critical reinforcement volume fraction above which the porosity of composites made by the
admixture method increases abruptly is 60% Mo, 42% TiB2 and 33% SiC. This fraction increases with decreasing aspect ratio
of the reinforcement. Among Cu/Mo, Cu/TiB2 and Cu/SiC at the same reinforcement volume fraction (50%), Cu/Mo gave the lowest
CTE, highest thermal conductivity and lowest electrical resistivity, while Cu/SiC gave the greatest hardness and Cu/TiB2 and
Cu/SiC gave the highest compressive yield strength. Compared to Cu/SiC, Cu/TiB2 exhibited much higher thermal conductivity
and much lower electrical resistivity.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
2.
Combustion reaction welding, one promising method to weld ceramics and metals, was used to weld TiB2 and Mo. The results showed that the reacted products through combustion reaction were TiB2 and MoB when the Mo contents in reactants were 20 wt pct and 40 wt pct while there was Mo besides MoB and TiB2 when there were 60 wt pct and 80 wt pct Mo in reactants. Diffusion of elements occurred at the interfaces of the two substrates. The interfaces between the reacted and the two substrates were indistinct after being welded. The welding temperature strongly affected properties of the samples. The value of bending strength of the sample with 80 wt pct Mo in reactant welded at 1500℃ was the highest, 368.52 MPa. The highest value of shear strength among all the samples was that of the one with 40 wt pct Mo in reactant welded at 1500℃, 50.97 MPa. 相似文献
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TiAl-B合金凝固过程中初生TiB2的固-液界面形态演变特征 总被引:2,自引:0,他引:2
用原位自生法制备了TiAl-B合金,并用XRD、SEM对材料的相组成、微观组织和初生TiB2晶体的界面结构特征进行了研究。结果表明:该合金主要由TiAl和TiB2两相组成;初生TiB2呈六面棱柱状,在其(0001)面存在清晰的生长台阶,凸台状或柱棒状分枝,它们的各晶面取向与母体的取向一致。分析表明,在TiAl-B合金凝固过程中初生TiB2晶体的固-液界面是不稳定的,使固-液界面由一完整光滑的界面逐渐演变为由多个相互独立的次级界面构成的复杂界面,次级界面亦为小面结构,具有相同的晶面取向关系。 相似文献
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用原位自生法制备了Ti-54Al-xB (at%)合金并利用XRD,SEM对合金的相组成和微观组织进行了研究。结果表明:片状TiB2基面存在与[0001]晶向平行的细棒状分枝,表面存在与[0001]晶向垂直的薄片凸耳状分枝,它们的晶体学取向与母体的取向一致。片状TiB2厚度一般小于0.3μm,表面上的凸耳状分枝厚度一般小于0.1 μm。分析表明,在不平衡凝固条件下,片状TiB2固-液界面前沿产生的富Al边界层和随着片状TiB2晶体的长大导致固-液界面上B原子过饱和度不均匀性增加的共同作用使固-液界面失稳,从而形成了片状TiB2的这种表面结构。 相似文献
7.
采用SHS/QP工艺制备了(TiB2+Fe)/Fe叠层材料。SEM分析表明TiB2+Fe金属陶瓷层结构致密。用EPMA研究了TiB2+Fe金属陶瓷层与Fe基片之间的界面连接机制,结果表明TiB2从TiB2+Fe侧向Fe基片侧进行扩散,以及TiB2+Fe层中的Fe粘结相和Fe基片的粘接完成了(TiB2+Fe)/Fe叠层材料的界面连接。叠层材料接头断裂时,断裂位置发生在TiB2+Fe金属陶瓷层,而不是沿着TiB2+Fe层与Fe基片的界面断裂。 相似文献
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Haibo Feng Yu Zhou Dechang Jia Qingchang Meng 《Materials Science and Engineering: A》2005,390(1-2):344-349
The in situ TiB/Ti–4.0Fe–7.3Mo composites were fabricated by plasma spark sintering (SPS) technique using mechanical alloying of Ti, Fe65Mo and B powder. The effects of sintering temperature on densification of the composites and microstructure of the in situ synthesized TiB were investigated using scanning electron microscope (SEM) and transmission electron microscope (TEM). A dense composite was obtained after sintering at 1000 °C for 5 min. Under proper ball milling and SPS conditions in situ TiB reinforced Ti–4.0Fe–7.3Mo composites have been prepared. The in situ TiB showed a typical needle shape grow along [0 1 0] direction. The transverse cross-section of TiB grain is a hexagonal shape with the planes of (1 0 0), (1 0 1) and . The stacking faults in the (1 0 0) plane were observed in the TiB needles. 相似文献
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采用原位自生法制备了Ti-17Al-1.5B复合材料,并用XRD、SEM对复合材料的相组成和微观组织进行了研究。结果表明:该合金由Ti3Al和TiB两相组成。初生TiB多呈较粗长的空心管状,共晶TiB呈短纤维状。根据晶体生长的固-液界面稳定性理论分析认为:TiB的B27晶体结构和晶体生长过程中的棱边效应导致初生TiB容易生长成空心管状。这是因为,在初生TiB晶体的[010]方向的固-液界面生长至一临界尺寸以后,晶面中心处因扩散受阻(热扩散和溶质扩散)而存在非常大的扩散过冷使晶面中心的台阶停止生长,这时TiB优先在棱边处长大;另外,TiB [010]方向生长速度非常快。二者的共同作用使初生TiB易于长成与 方向一致的空心管状。而共晶TiB则由于径向尺寸很小(呈纤维状),不易于长成空心管状。 相似文献
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Jinyong ZHANG+ Zhengyi FU Weimin WANGState Key Lab of Advanced Technology for Materials Synthesis Processing Wuhan University of Technology Wuhan China 《材料科学技术学报》2005,21(6):841-844
1. IntroductionTitanium diboride ceramic has some special proper-ties, such as high melting points, high hardness, highelectrical and thermal conductivity. These special prop-erties make it has a great potential to be used as contactmaterials. However, this application is still limited forpoor sinterability and brittle of TiB2[1~3]. To improve itssinterability and toughness, some metals were selected asadditives for liquid phase sintering of TiB2. Metals likeFe, Co and Ni were studied in m… 相似文献
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提出一种新型的原位反应合成工艺——熔体反应法, 以TiO2、H3BO3、Na3AlF6 和Al-Cu 合金为原材料, 采用熔体反应法制备了低成本的内生颗粒增强Al-4. 5Cu/TiB2 复合材料。TiB2 颗粒细小, 平均尺寸为0. 93 Lm, 均匀分布于基体之中, 与基体结合良好。当TiB2 的含量为10 vo l% 时, 复合材料的抗拉强度为416. 7M Pa, 屈服强度为316.9M Pa, 延伸率为3. 3%。 相似文献
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采用热等静压(HIP)工艺,把包复在真空玻璃容器内的C/Al复合丝热压成致密的C/Al复合材料。用扫描电镜(SEM)观察到复合材料的低强度平断口和界面反应层。运用透射电镜(TEM)和X射线能谱仪(XES)观察和确定界面的形貌和成分,发现界面分成层状,界面层的TiB2向两边扩散,而纤维和基体的成分则通过界面而互相扩散。另外,还用电子衍射技术(EDT)研究了界面的晶体结构,确定它的相组成为TiO2、TiC、TiB2、γ-Al2O3及Ti、B和C等。采用俄歇电子能谱(AES)分析了界面区的化学组分,并运用二次离子质量谱(STMS)确定出界面的化学组成,除发现Al4C3,与EDT的结果基本一致。 相似文献
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将Ti合金插层引入(Ti+B_4C)反应原料和Ti合金底板之间,研究Ti合金插层厚度变化对超重力反应连接TiB2基陶瓷/Ti-6Al-4V梯度复合材料界面显微组织与力学性能的影响。热力学计算表明:合成反应的绝热温度远超Ti合金的熔点,可以保证不同厚度的Ti合金插层全部熔化。XRD、FESEM及EDS分析结果表明:在陶瓷和Ti合金底板之间形成梯度界面区,且随着Ti合金插层厚度的增加,梯度界面区的厚度也不断增大。自陶瓷基体至Ti合金底板,TiB_2和TiC_(1-x)的体积分数不断减少,而TiB的体积分数先增加而后减少,最终形成以TiB_2、TiC_(1-x)及TiB陶瓷相尺寸和分布为特征的梯度复合结构。而梯度连接区的硬度分布趋势更加平缓,其剪切强度不断提升。 相似文献
15.
采用SEM、EDS和XRD等测试手段研究了粉末原位合成法制备的Mg-50%TiB2(质量分数,下同)中间合金的组织和结构,以及Mg-50%TiB2和Sr对AZ91D镁合金显微组织的细化效果。结果表明,1.4%(Mg-50%TiB2)中间合金和0.1%Sr的复合添加可使AZ91D镁合金的α-Mg晶粒尺寸由基体合金的240μm降至49μm。通过面错配度计算证实TiB2可成为初生-αMg的良好异质核心。加入碱土元素Sr引起合金成分过冷度增加,从而激活固/液界面前沿潜在的TiB2核心,提高TiB2的形核率。 相似文献
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研究了XD工艺原位生成NiAlFe-TiB2复合材料的显微组织和界面结构,分析了Fe对材料压缩性能的影响及微观机制,加入25%Fe元素后,形成的Fe(Ni,Al,Ti)新相以枝晶间的形式连接于基体之间以及基体与增强颗粒之间,提高了材料的塑性。运用高分辨电力显微术分析研究了压缩变形后增强颗粒与基体的界面。 相似文献
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TiB2, pyrolytic carbon (Cpyr) and Cpyr + TiB2 double layer coatings have been envisaged as potential protective coatings to prevent the deleterious interface reactions between the carbon fibre and the aluminium matrix during composite manufacturing. These coatings have been obtained by low pressure chemical vapour deposition on T800H carbon fibre yarns. In spite of a 20 % increase in the coated monofilaments tensile strength observed for very thin Cpyr coatings, a strength decrease as a function of the coating thickness is recorded for single Cpyr or TiB2 layers. For the TiB2 coatings, this decrease fits well with Ochiai's model which simulates the notch effect induced by a cracked brittle layer. Concerning the Cpyr coatings, a lower damaging effect is observed as compared to TiB2, it may be explained by the difference between the Young's moduli of both layers. Although the initial fibre properties are not perfectly maintained in the case of the double layer, the crack deviation role of the Cpyr coating succeeds in preserving the coated fibres from the TiB2 notch effect, thus leading to a noticeable strength increase. 相似文献
19.
《Composites Part A》1999,30(10):1209-1214
Interfacial processes in SCS-6 SiC/TiB2/Super α2 composites were investigated by means of analytical transmission electron microscopy (TEM). No reaction between the TiB2 coating and the carbon coating of the fibres can be found in the as-processed specimen. At the TiB2/matrix interface the TiB2 transforms into both a homogeneous layer and needles of TiB which are distributed in the matrix. This process takes place according to the reaction TiB2+Ti=2TiB. The TiB2 coating is consumed completely in the specimen heat treated at 900°C for 64 h. At this time TiC and Ti3AlC form at the TiB/C-coating and the TiB/matrix interface, respectively. Prolonging the holding time at 900°C, reaction layers thicken continuously following parabolic reaction kinetics. The paper additionally discusses the formation mechanisms of the reaction products. 相似文献
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采用等离子喷涂法制备出Al/TiB_2电极。运用SEM、XRD表征复合电极界面的组织形貌和物相结构,研究在相同送粉电位、喷涂距离条件下不同喷涂功率对复合电极界面电阻率及电化学性能的影响。结果表明:等离子喷涂法制备的Al/TiB_2复合电极表面涂层的物相组成为TiB_2。喷涂后的TiB_2可均匀致密地涂在Al基体表面,但并未与Al发生界面反应,而是形成机械式结合。当喷涂功率、送粉电位和喷涂距离分别为34kW、12V、10cm时试样界面电阻率最小为1.22×10~(-6)Ω·cm,较Ti/Al电极降低66%,腐蚀电流密度(1.47×10~(-4) A/cm~2)较Ti/Al电极降低81%,腐蚀电压(-0.579V)较Ti/Al电极增加35%,其耐腐蚀性能达到最好。 相似文献