Absolute stability of the solidification interface in a laser resolidified Zn-2wt.%Cu hypoperitectic alloy

• 来源期刊: 中国物理（英文版）
• 关键词: rapid solidification absolute stability laser surface resolidification Zn-Cu peritectic alloy
• 年，卷（期）: 2006,（7）
• 页码范围: 1631-1637
• 页数: 7页
• 语种: 英文

摘要

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 η phase. This indicates that HGAS was successfully achieved in the present experiments.