Guoqing CHEN
,
Kaifeng ZHANG
,
Guofeng WANG
,
Y
,
ong YU
材料科学技术（英文）
Numerical simulation of hot-press sintering of nano-sized ceramic powders was introduced by the commercial finite element code MSC.MARC. The powder plastic model and the thermo-mechanical coupled quadrilateral element were developed and adopted in the simulation. The mechanical and thermal properties of the nano-sized alumina based powders were determined. In addition, the experimental research and numerical simulation of the sintering process of different initial densities were carried out. The stress state in sintering of green compacts with different initial densities was analyzed by the densification theory. The reason for the density fluctuations of as-sintered ceramic bulks was found out.
关键词:
Sintering
,
null
,
null
,
null
Wenbo HAN
,
Kaifeng ZHANG
,
Guofeng WANG
,
Xiaojun ZHANG
材料科学技术（英文）
Superplastic forming and diffusion bonding (SPF/DB) is a well-established process for the manufacture of components almost exclusively from Ti-6Al-4V sheet material. The sandwich structure of Ti-6Al-4V alloy is investigated. The effects of the microstructure on the SPF/DB process were discussed. The microstructure at the interfaces and the distribution of thickness were researched.
关键词:
Superplastic forming
,
null
,
null
,
null
Xifeng LI
,
Kaifeng ZHANG
,
Changli WANG
,
Wenbo HAN
,
Guofeng WANG
材料科学技术（英文）
The amorphous Fe78Si9B13 ribbons were bend stress relaxed at various temperature well below the crystallization temperature (Tx) for different time. The effect of pre-annealing on the subsequent bend stress relaxation was examined. The variation of the microstructure and microhardness during bend stress relaxation process was studied using X-ray diffraction (XRD), atomic force microscopy (AFM) and Vickers microhardness test, respectively. Curvature radius of the amorphous Fe78Si9B13 ribbons decreased with increase bend stress relaxation temperature and time. The microhardness of the stress relaxed specimens increased with time at 300℃ due to the forming of nanocrystals during bend stress relaxation. The pre-annealing reduced the decrease rate of the curvature radius of stress relaxed specimens.
关键词:
Bend stress relaxation
,
null
,
null
,
null
Guoqing CHEN
,
Kaifeng ZHANG
,
Wenbo HAN
,
Junting LUO
材料科学技术（英文）
A series of alumina-zirconia composites with various grain sizes were prepared from the nano-sized powders with different agglomerations. Microstructural analysis of the sintered compacts indicates that the as-sintered material is a typical intra/inter granular nanocomposite with uniform distribution of the zirconia grains in the alumina matrix. Superplastic deep drawing test under different conditions demonstrates that dense Al2O3/ZrO2 samples with average grain size of 230 nm can be elongated to a dome height of at least 12 mm at the punch rate of 0.6 mm•min-1 at 1400℃. Further drawing tests show that for the composites with larger grain size, such elongation cannot be achieved at such a strain rate.
关键词:
Nanocomposite
,
null
,
null
,
null
Xifeng LI
,
Kaifeng ZHANG
,
Guofeng WANG
材料科学技术（英文）
The paper reports on the observation of nanoscale morphology on the tensile fracture surface of a brittle amorphous Fe-based ribbon. The formation of nanoscale damage cavity structure is a main characteristic morphology on the fracture surfaces. Approaching the ribbon boundary, these damage cavities assemble and form the nanoscale periodic corrugations, which are neither Wallner lines nor crack front waves. The periodic corrugations result from the interactions between the reflected elastic waves by the boundaries of amorphous ribbon and the stress fields of the crack tip.
关键词:
Nanoscale periodic corrugation
,
断裂空洞
,
拉伸断裂
Guofeng WANG
,
Kaifeng ZHANG
,
Dezhong WU
材料科学技术（英文）
Nano-sized 3Y-TZP powders were Synthesized by two methods. A fractal software was developed. A new and convenient method for characterizing the quality of Synthetic process by using fractal theory was obtained.
关键词:
