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1.
TiB reinforced titanium composites have been successfully synthesized by adding the Al/TiB2 master alloy into titanium alloy. The phase constituent and the microstructure have been studied by XRD and SEM. Compared with the standard values, the lattice parameter of TiB calculated from the XRD pattern indicates that the synthesized TiB is of prefect crystal structure. The microstructure has shown that high aspect ratio fibrous TiB has been found, which homogeneously distribute in the matrix in a random way. The size is about 100 μm in length, less than 2.5 μm in diameter and the aspect ratio is greater than 40. Deep etched microstructures show that some coarse hollow TiB corresponding to primary TiB are also formed with smooth and flat surface and random transverse section. The size is about 100 μm in length and greater than 10 mum in diameter. The solidification process has also been analyzed.  相似文献   

2.
The oxidation behavior of an in situ TiB short fibre reinforced Ti-6Al-1.2B alloy was investigated in a flowing air over the temperature range 873–1223 K. The alloy exhibited a parabolic oxidation behavior with the activation energy of 250 kJ/mol, which was supposed to be mainly controlled by the inward diffusion of oxygen. The oxide scales consisted mainly of TiO2, a small amount of Al2O3 and amorphous B2O3. The morphology of TiO2 changed from fine needle-shape at 1023 K to fine sphere at 1073 K and then well-developed block at a higher temperature. The microstructure of the subsurface showed that B2O3 pores and crack appear at the Ti/TiB interface above 1023 K as a result of the oxidation of TiB and evaporation B2O3. Combined with the thermodynamic analysis, it was suggested that the presence of TiB and formation of B2O3 could not act as an oxidation resistance. Finally, the diffusion coefficient of oxygen in Ti-6Al-1.2B exposure to 1073 K in air was determined to be 4.22 × 10–11 cm2/s.  相似文献   

3.
Microstructure of XDTM Ti-6Al/TiC composites   总被引:1,自引:0,他引:1  
XDTM method has been used to prepare TiC particles reinforced titanium composites. The phases constitute and microstructure of the Ti-6Al/TiC composites have been investigated by XRD and SEM. The lattice parameter value of TiC calculated from the XRD pattern has indicated that there exists carbon deficiency in TiC. The microstructure observed by SEM has shown that TiC is of dendritical and spherical morphology, which quite different from that of the TiC in Al/TiC master alloy. In macrostructure, the TiC particles homogeneously distribute in the matrix, but the spherical TiC mainly segregate at the grain boundary, especially at the triangle grain boundary. Microstructure of the interface has also been observed by TEM and HTEM. No reaction product has been found in the interface, but a C atom diffusion layer was determined by energy spectrum diffraction and observed by HREM image of interface microstructure. Although no definite crystallographic relationship can be defined, a orientation relationship of [0110]Ti//[011]TiC has been obtained.  相似文献   

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TiC+TiB2协同增强Al-Cu原位复合材料   总被引:1,自引:0,他引:1  
为利用TiC和TiB2的协同增强作用,采用基于熔体接触反应法和混合盐反应法的新工艺"两步法"制备了(TiC TiB2)/Al-2Cu原位复合材料.利用扫描电子显微镜及差式扫描量热计对热处理前后的原位复合材料进行了组织及热分析,结果表明:组织中两相粒子的分布比单相粒子增强的情况更加均匀,而且T4处理实现了两相粒子真正意义上的均匀相间分布;相对于单一的Al-2Cu合金,(TiC TiB2)/Al-2Cu的熔化开始温度和凝固开始温度升高,熔化潜热和凝固潜热增大,体系稳定性从而得以提高,T4处理进一步增大了这一趋势.  相似文献   

7.
Abstract

Duplex metal (Cu/Mo and Cu/W) coated SiC(SCS–6) fibre reinforced Ti-15-3 matrix composites have been prepared using a hot isostatic pressing process. The effect of the duplex metal coatings on the fatigue behaviour of unnotched SiC(SCS–6) fibre reinforced Ti-15-3 matrix composite has been studied. The fatigue resistance of this fibre reinforced composite is improved by use of the duplex metal coatings. The Cu/Mo and Cu/W duplex metal coating layers prevent debonding of the SCS coating layer from the SiC fibre surface, thus also effectively preventing a reduction in strength of the fibre. During the fatigue test, fibre bridging behind the matrix crack tip reduces the crack growth rate of the matrix; this mechanism is difficult to achieve with the pristine fibre composite. Evolution of the fatigue damage can be quantitatively evaluated by means of a fatigue damage parameter. Matrix crack propagation is the dominant factor responsible for the increase in damage parameter of the composites.  相似文献   

8.
A new process of preparing particulate-reinforced ceramic composites by internal synthesis has been developed. SiC powder mixed with TiN and amorphous boron was hot-pressed above 2000° C in an argon atmosphere. The boron molar content in the mixture was designed to be more than twice that of TiN. In the process of hot-pressing, the following reaction took place between 1100 and 1700° C TiN+2B TiB2+1/2N2 The synthesis of TiB2 was followed by the densification of SiC matrix with the aid of the excess boron. The new process provides SiC matrix composites in which fine TiB2 particulates are dispersed. Compared with hot-pressed monolithic SiC, the composite containing 20 vol % TiB2 exhibits a 80% increase in fracture toughness and about the same flexural strength of 490 MPa at 20° C in air and 750 MPa at 1400° C in a vacuum.  相似文献   

9.
A novel hot-pressing technique for the manufacturing of basalt fibre reinforced glass matrix composites was investigated. Two-dimensional (2D) fibre mats were sandwiched between borosilicate glass powder layers, thus configuring a much simpler processing route than that commonly employed for the production of fibre-reinforced glasses. Besides economic benefits, the use of fibre mats may lead to technologic advantages due to the possibility of readily coating the fibres with a suitable material (e.g. titanium oxide) by means of the sol-gel method. The coating of basalt fibre mats with TiO2 is proposed for preventing the fibres from an excessive adhesion to the glass matrix. The developed composites containing 15 vol% of 2D-fibre reinforcement exhibited promising bending strength (∼90 MPa) and desirable “graceful” fracture behaviour without catastrophic failure. Thus the present study represents a convenient approach for production of advanced low-cost fibre reinforced glass matrix composites for structural applications.  相似文献   

10.
Geopolymer matrix composites reinforced with different volume fractions of short carbon fibres (Cf/geopolymer composites) were prepared and the mechanical properties, fracture behaviour and microstructure of as-prepared composites were studied and correlated with fibre content. The results show that short carbon fibres have a great strengthening and toughening effect at low volume percentages of fibres (3·5 and 4·5 vol.%). With the increase of fibre content, the strengthening and toughening effect of short carbon fibres reduce, possibly due to fibre damage, formation of high shear stresses at intersect between fibres and strong interface cohesion of fibre/matrix under higher forming pressure. The property improvements are primarily based on the network structure of short carbon fibre preform and the predominant strengthening and toughening mechanisms are attributed to the apparent fibre bridging and pulling-out effect.  相似文献   

11.
Thermal fatigue resistance is one of the most important parameters to design engine materials. The thermal fatigue crack growth behavior of alumina short fibre (V f = 18 vol.%) reinforced AlSi12CuMgNi aluminum alloy composite has been investigated under thermal cycling condition between room temperature and 280 °C. Initiation and propagation of thermal fatigue crack have also been discussed. The results show that in the range of short crack, the fibres play an important role in the path of thermal fatigue crack, and the crack propagation rate of composites is much larger than that of the matrix alloy.  相似文献   

12.
The properties of two types of short carbon fibre (CF) reinforced thermoplastic resin composites (CF-PPS and CF-PES-C), such as strength (y). Young's modulus (E) and fracture toughness (K 1c), have been determined for various volume fractions (V f) of CF. The results show that the Young's modulus increases linearly with increasingV f with a Krenchel efficiency factor of 0.05, whereas y andK 1c increase at first and then peak at a volume fraction of about 0.25. The experimental results are explained using the characteristics of fibre-matrix adhesion deduced from the load-displacement curves and fractography. By using a crack pinning model, the effective crack tensions (T) have been calculated for both composites and they are 57 kJ m–1 for CF-PPS and 4.2 kJ m–1 for CF-PES-C. The results indicate that the main contribution to the crack extension originates from localized plastic deformation of the matrix adjacent to the fibre-matrix interface.  相似文献   

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纤维增强聚合物基复合材料的低温性能   总被引:2,自引:0,他引:2  
对纤维增强聚合物基复合材料在低温领域的实际应用进行了分类介绍,通过对纤维增强聚合物基复合材料的低温性能、性能影响因素和作用机理、低温应用安全性等方面的研究工作进行总结,突出各类纤维增强聚合物基复合材料低温下的性能优势,阐明了材料性能的不足之处及相应改进措施.对于实际低温应用中纤维增强聚合物基复合材料的选择、性能设计优化,系统安全性的增强提供了参考作用.  相似文献   

15.
In the study, fracture behaviour of short bamboo fibre reinforced polyester composites is investigated. The matrix is reinforced with fibres ranging from 10 to 50, 30 to 50 and 30 to 60 vol.% at increments of 10 vol.% for bamboo fibres at 4, 7 and 10 mm lengths respectively. The results reveal that at 4 mm of fibre length, the increment in fibre content deteriorates the fracture toughness. As for 7 and 10 mm fibre lengths, positive effect of fibre reinforcement is observed. The optimum fibre content is found to be at 40 vol.% for 7 mm fibre and 50 vol.% for 10 mm fibre. The highest fracture toughness is achieved at 10 mm/50 vol.% fibre reinforced composite, with 340% of improvement compared to neat polyester. Fractured surfaces investigated through the Scanning Electron Microscopy (SEM) describing different failure mechanisms are also reported.  相似文献   

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Valid plane-stress fracture toughness evaluation of short fibre reinforced composites relies essentially on the successful separation of the energy absorbed in the localized crack-tip region out of the total energy absorbed by the cracked material body at large. Three different experimental techniques, all stemming from the energetic interpretation of theJ integral, are utilized and their relative merits in the characterization of fracture initiation in short glass fibre reinforced injection-moulded nylon 6.6 examined. Various theoretical aspects concerning these experimental methods are outlined. The rationale behind using a single-edge-notched tension type specimen for theJ c test is presented. TheJ c value obtained from the compliance calibration method and the quasistatic energy method agree closely and can be considered to be independent of pre-crack length and specimen geometry when the pre-crack length to specimen width ratio (a/w) is larger than 0.45. The extrapolation method fails nevertheless to yield a physically consistentJ c value, possibly due to its questionable theoretical representation. As no constraint on boundary conditions is necessitated during the course of crack extension, the quasistatic energy is physically more appealing.  相似文献   

18.
Impression creep behaviour of the powder metallurgy processed steel matrix composites was investigated under constant stress at different temperatures in the range of 873–973?K. By using the power-law relationship, the estimated activation energy for unreinforced steel was found to be 149?kJ?mol?1 and steel reinforced with 2 and 4?vol.-% TiB2 was found to be 298 and 338?kJ?mol?1, respectively indicating better creep resistance of the reinforced steel matrix composites. Dislocation creep is the dominant creep mechanism based on the calculated values of stress exponent and activation energy. Hence, this method can be used to assess the potential of steel matrix composites for use as structural materials for high-temperature application.  相似文献   

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Chen  Y. D.  Li  Z. C.  Dan  C. Y.  Chen  Y. C.  Wang  H. W.  Wang  L.  Liu  J.  Wu  Y.  Chen  Z. 《Journal of Materials Science》2022,57(3):1778-1795
Journal of Materials Science - Abnormal grain growth behaviors of in situ TiB2 particle-reinforced Al composites under two-step annealing are investigated in this study. Abnormal grain growth...  相似文献   

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