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
Zhaohua JIANG
,
Xuetong SUN
,
Yanping LI
,
Fuping WANG
,
Y
,
ong LÜ
材料科学技术（英文）
Ceramic coatings were prepared on Ti-6Al-4V alloy using ac micro-arc oxidation (MAO) in silicate-hypophosphate solution. Growth regularity and formation mechanism of ceramic coatings were discussed. It was found that during the first stage the growth rate of coatings toward the external surface was larger than that toward substrate and then the coating began to grow mainly towards Ti alloy. When the total coating thickness reaches a certain value, it would no longer increase. In addition, the variations of the composition and microstructure of ceramic coatings according to the depositing time were also investigated with X-ray diffraction (XRD) and scanning electron microscope (SEM). The amount of rutile TiO2 gradually increased, whereas the amounts of the anatase TiO2 and amorphous phases first increased and then decreased slightly.
关键词:
Titanium alloy
,
null
,
null
,
null
Min XU
,
Minxiu QUAN
,
Zhuangqi HU
,
Y
,
ong WANG
,
Liang ZUO
材料科学技术（英文）
Fe62Co8-xCrxZr6Nb4B20(x=0–4 at. pct) metallic glasses show high thermal stability with a maximum supercooled liquid region of about 84.8 K. The addition of 2 at. pct Cr causes the extension of the supercooled liquid region remarkably, leading to the enhancement of thermal stability and glass-forming ability. The crystallization of the Fe-based glassy alloys takes place through a single exothermic reaction, accompanying the precipitation of more than three kinds of crystallized phases such as α-Fe, Fe2Zr and ZrB2. The long-range atomic rearrangements required for the precipitation of the multiple crystalline phases seem to play an important role in the appearance of the large supercooled liquid region through the retardation of the crystallization reactions. The Fe-based alloys exhibit soft ferromagnetic properties. The saturation magnetization decreases with increasing Cr content while the saturated magnetostriction increases as a function of Cr content. There is no distinct change in the saturation magnetization and coercive force with annealing temperature below the crystallization temperature. The devitrification gives rise to a considerable enhancement in both δs and Hc.
关键词:
Cr addition
,
null
,
null
Yan CHEN
,
Y
,
ong GONG
材料科学技术（英文）
The magnetic abrasive machining is a method that the magnetic field (lines of magnetic force) is used to precisely machine the surface of the workpiece. When it is a magnetic workpiece, and the workpiece is magnetized and then becomes a new magnetic pole. On the contrary, when it is nonmagnetic workpiece, it can not be magnetized. In this research, the precise processing phenomenon and the condition on a shaft with steps are examined based on the experiment result mentioned above.
关键词:
Magnetic abrasives machining
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null
,
null
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