Chun-Nian He
,
Chao Feng
,
Ji-Chuan Lin
,
En-Zuo Liu
,
Chun-Sheng Shi
,
Jia-Jun Li
,
Nai-Qin Zhao
金属学报(英文版)
doi:10.1007/s40195-016-0376-3
Carbon nanotube (CNT)-reinforced 6061Al alloy matrix composites were prepared by chemical vapor deposition (CVD) combined with hot extrusion technique. During the preparation process, the 6061Al flakes obtained by ball milling of the 6061Al spherical powders were subjected to surface modification to introduce a hydrophilic polyvinyl alcohol (PVA) membrane on their surface (6061Al@PVA) to bond strongly with nickel acetate [Ni(II)]. Then the 6061Al@PVA flakes bonded with Ni(II) were calcined and reduced to Ni nanoparticles, which were then heat-treated at 580 °C to remove PVA for obtaining even Ni/6061Al catalyst. After that, the as-obtained Ni/6061Al catalyst was employed to synthesize CNTs on the surface of the 6061Al flakes by CVD. After hot extrusion of the CNT/6061Al composite powders, the as-obtained CNT/6061Al bulk composites with 2.26 wt% CNTs exhibited 135% increase in yield strength and 84.5% increase in tensile strength compared to pristine 6061Al matrix.
关键词:
Metal
,
matrix
,
composites
,
(MMCs)
,
Microstructure
,
Mechanical
,
properties
,
Carbon
Applied Physics Letters
The magnetoelectric Tb-Fe/Pb(Zr(0.52)Ti(0.48))O(3) thin-film heterostructure was prepared by low energy cluster beam deposition. The microstructures, ferroelectric property, leakage current, and magnetization, as well as magnetoelectric effect were investigated for the heterostructure. It is shown that the thin-film heterostructure displays the well-defined microstructure with clear interface. The heterostructure not only exhibits good ferromagnetic and ferroelectric properties, but also possesses strong magnetoelectric effect. The present work provides an ideal avenue to prepare magnetoelectric composite films and facilitates their applications on the microelectromechanical system devices. (C) 2008 American Institute of Physics.
关键词:
composites
Zhenzhong CHEN
,
Ping HE
材料科学技术（英文）
Fatigue crack propagation (FCP) behaviors were studied to understand the role of SiC particles in 10 wt pct SiCp/A2024 composites and Si particles in casting aluminum alloy A356. The results show that a few particles appeared on the fracture surfaces in SiCp/Al composites even at high △K region, which indicates that cracks propagated predominantly within the matrix avoiding SiC particles due to the high strength of the particles and the strong particle/matrix interface. In casting aluminum alloy, Si particle debonding was more prominent. Compared with SiCp/Al composite, the casting aluminum alloy exhibited lower FCP rates, but had a slight steeper slope in the Paris region. Crack deflection and branching were found to be more remarkable in the casting aluminum alloy than that in the SiCp/Al composites, which may be contributed to higher FCP resistance in casting aluminum alloy.
关键词:
Aluminum-matrix composites
,
composites
,
casting
,
alloy
Nanostructured Materials
Nanocrystalline compound TiC has been synthesized by mechanically alloying (MA) the starting Ti-50 at.% C powder mixtures. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to analyze the structural evolution of Ti50C50 during milling. The changes of the grain size and the internal strain for different phases were determined as a function of milling time. Under the employed condition, TiC formed when milling for 10 h and its amount increased with milling time. After 27 h milling, TiC formed completely with a grain size of 9 nm, which was ill good agreement with the TEM observation, and the internal strain of TiC reached 2.4%. It is suggested that the reaction is controlled by the interdiffusion of elements, especially the contribution of C atoms. The large negative heat of formation for TiC nor only provides a driving force to the reaction but also favors the reaction by increasing the diffusivity of C atoms.
关键词:
composites
Materials Science and Technology
An ultrasonic liquid infiltration technique has been developed for the fabrication of carbon fibre reinforced aluminium (CF/Al) precursor wires. The principal effect of ultrasound on aluminium infiltration into carbon fibres is considered to be caused by cavitation. The acoustic power required to produce cavitation in the present experimental system has been approximately calculated ta be about 150 W which is much greater than the requirement, several tens of watts, for overcoming the capillary pressure among carbon fibres. The observations on the morphology of the CF/Al precursor wires show that there are generally four states of infiltration: totally non-infiltrated, non-infiltrated in the centre and in some local regions of the wires, and completely infiltrated. It is found that carbon fibres can be sufficiently impregnated by molten aluminium given the appropriate application of ultrasound. Furthermore, a single fibre tensile test shows that there is no strength degradation of carbon fibres after aluminium infiltration. The CF/Al precursor wires obtained have an average fibre volume fraction of 26%. The maximum longitudinal tensile strength of the CF/Al wires is 605 MN m(-2), which implies a fibre strength transfer efficiency of 0.76.
关键词:
composites
GUO Shuqi HAN Guihuan YAO Zhongkai Harbin Institute of Technologh
,
Harbin
,
China YAO Zhongkai Dept.of Metals and Technology
,
Harbin Institute of Technology
,
Harbin
,
China
金属学报(英文版)
This paper presents an investigation on the microstructures and properties of the 17v.-% SiCw/Al-12Si composites.TEM observations and EDAX analysis revealed that Al diffuses into the SiC whiskers and that dislocations exist at the whisker/matrix interfaces. Tensile test results showed that the isothermal exposure and thermal cycle at both 573K and 733 K caused the UTS reduction of the composites,and the reduction in UTS due to thermal exposure at 733 K was much more significant than that due to thermal cycle at the same tem- perature.The SiC_W/Al-12Si composites were also found to have exellent wear resistance, which does not seem to vary much with the volume content of whiskers in the ronge of 11— 17%.
关键词:
composites
,
null
,
null
,
null
Liqing CHEN
材料科学技术（英文）
The 42.1 vol. pct TiC/AZ91D magnesium-matrix composites with interpenetrating networks were fabricated by in-situ reactive infiltration process. The compressive creep behavior of as-synthesized composites was investigated at temperature ranging from 673 to 723 K under loads of 95-108 MPa. For a comparative purpose, the creep behavior of the monolithic matrix alloy AZ91D was also conducted under loads of 15-55 MPa at 548-598 K. The creep mechanisms were theoretically analyzed based on the power-law relation. The results showed that the creep rates of both TiC/AZ91D composites and AZ91D alloy increase with increasing the temperature and load. The TiC/AZ91D composites possess superior creep resistance as compared with the AZ91D alloy. At deformation temperature below 573 K, the stress exponent n of AZ91D alloy approaches theoretical value of 5, which suggests that the creep process is controlled by dislocation climb. At 598 K, the stress exponent of AZ91D is close to 3, in which viscous non-basal slip deformation plays a key role in the process of creep deformation. However, the case differs from that of AZ91D alloy when the stress exponent n of TiC/AZ91D composites exceeds 9, which shows that there exists threshold stress in the creep process of the composites, similar to other types of composites. The average activation energies for the creep of the AZ91D alloy and TiC/AZ91D composites were calculated to be 144 and 152 kJ/mol, respectively. The existence of threshold stress in the creep process of the composites leads to an increase in activation energy for creep.
关键词:
Magnesium-matrix composites
,
composites
,
TiC/AZ91D
,
in
