Absolute stability of the solidification interface in a laser resolidified Zn--2wt.%Cu hypoperitectic alloy |
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Authors: | Su Yun-Peng Lin Xin Wang Meng Xue Lei and Huang Wei-Dong |
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Institution: | State Key Laboratory of Solidification Processing,Northwestern Polytechnical University, Xi'an 710072, China |
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Abstract: | This paper reports on laser surface remelting experiments performed on a
Zn--2wt.%}Cu hypoperitectic alloy by employing a 5kW CW CO2 laser at
scanning velocities between 6 and 1207mm/s. The growth velocities of the
microstructures in the laser molten pool were accurately measured. The planar
interface structure caused by the high velocity absolute stability
was achieved at a growth velocity of 210~mm/s. An implicit expression
of the critical solidification velocity for the cellular--planar transition was
carried out by nonlinear stability analyses of the planar interface. The results
showed a better agreement with the measured critical velocity than that predicted by
M--S theory. Cell-free structures were observed throughout the whole molten pool at
a scanning velocity of 652~mm/s and the calculated minimum temperature gradient in
this molten pool was very close to the critical temperature gradient for high
gradient absolute stability (HGAS) of the \eta phase. This indicates that HGAS
was successfully achieved in the present experiments. |
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Keywords: | rapid solidification absolute stability laser surface resolidification Zn--Cu peritectic alloy |
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