J.B. Liu
,
L.J. Hu
,
Y.T. Wang
,
Z.Q. Liu
,
K. Miao
,
Z.L. Tian
金属学报(英文版)
The transformation behavior and microstructure development in the heat affected zone
(HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found that
the HAZ has intermediate temperature transformation characteristics in a wide range
of cooling rates, with the bainite sheaves consisting of bainite ferrite plates without
carbide precipitation and retained austenite in the fast cooling regime. At relatively
high cooling rates, which corresponded to low heat inputs, the hardness of the simulated
HAZ was above that of the base metal. When the cooling rate was below 9±C/s, the
welding HAZ would have an obvious softening. The analysis of transformation rates
in continuous cooling processes was completed by numerical differential method. The
result indicated that the microstructure transformation rate of the HAZ in 800MPa
grade ultra fine structured steel changed sharply to slow speeds when the cooling time
t8=5 is longer than 7s.
关键词:
ultra fine structured steel
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Z.G. Shang
,
Z.Q. Liu
,
P.J. Shang
,
J.K. Shang
材料科学技术（英文）
TiO2 nanowires were synthesized successfully in a large quantity by thermal evaporation using titanium monoxide powder as precursor. X-ray diffraction results showed that all the products were pure rutile phase of TiO2. According to microstructural observations, the nanowires have two typical morphologies, a long straight type and a short tortuous type. The straight nanowires were obtained at a wide temperature range of 900−1050 °C, while the tortuous ones were formed below 900 °C. Transmission electron microscopy characterization revealed that both the straight and the tortuous nanowires are single-crystal rutile TiO2. The preferential growth direction of the nanowires was determined as [110] orientation according to electron diffraction and high-resolution image analyses. The morphological change of TiO2 nanowires was discussed by considering the different atomic diffusion rates of Ti atoms caused by the phase transformation in Ti substrate at around 900 °C.
关键词:
Rutile-TiO2
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null
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null
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