LIU Zhiguo CHEN Yong CAO Yanni Nanjing University
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Nanjing
,
ChinaZHU Zhengsheng Shaanxi Iron and Steel Institute
,
Xi'an
,
China Professor
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Dept.of Physics
,
Nanjing
,
University
,
Nanjing 210008
,
China
金属学报(英文版)
The microstructural evolution and precipitation hardening of an Elinvar alloy doped with Ti and Al during isothermal aging at 700℃ have been investigated by atom probe field ion microscopy and microhardness measurements.The γ′ precipiates are spherical and coherent with the matrix.The chemical composition of the precipitates are(Ni_(0.53)Fe_(0.47)_3 (Ti_(0.(?))Al_(0.4)). During aging,a Lifshitz-Wagner type dissolution and coarsening reaction of the precipitates has been observed,The hardness of the material varies with the aging time and reaches maxi- mum when the average diameter of the precipitates was about 11 nm.
关键词:
Elinvar alloy
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LIU Junming LIU Zhiguo WU Zhuangchun Nanjing University
,
China LIU Junming
,
lecturer
,
National Laboratory of Solid State Microstructuros
,
Nanjing University
,
Nanjing 210008
,
China
金属学报(英文版)
The profile features of the solidifying interface of the irregular Al-Si eutectic during directional solidification are studied by numerically solving a nonlinear coupling equation of directional solidification of this eutectic.The critical splitting point of the solidifying interface coincides with the maximum value of its position and corresponds to the marginal stability point.Argument is presented that the interlamellar spacing for local regular structure selects the critical splitting state of the α(Al)-liquid interface as its operating point,and the oper- ating point of the average interflake spacing for the irregular structure is the critical splitting state of the β(Si)-liquid interface.The scaling laws derived,which have the more general forms than the classic Jackson-Hunt scaling,gained support from the experimental results.
关键词:
irregular Al-Si eutectic
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Junming LIU Zhiguo LIU Zhuangchun WU National Lab.of Solid State Microstructures
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Nanjing University
,
Nanjing 210008
,
China
材料科学技术（英）
As a simulation of surface solidification of materials,quasi-two dimensional dendritic deposition of ammonium chloride(NH_4Cl)crystals from an aqueous solution film with free surface by vapourization was investigated by the in- situ observation technique.The depositing morphologies of NH_4Cl crystals are faceted and of growth laws differing from the three-dimensional case.Under low supersaturation,faceted dendrites formed,whereas the anisotropy in growth kinetics decreases with the increase of supersaturation.When vapourizing rate(supersaturation)is not very low, oscillations of growth rate.tip-radius and second arm spacing of the dendrites were observed.It is suggested that this dynamic phenomenon is attributed to the correlation between the convection-transfer effect induced by the surface tension gradient of solution film.and the driving force for deposition.
关键词:
surface deposition
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