激光重熔熔池宏微观凝固过程的实时观察

In Situ Observation of Macro and Micro Solidification Process in the Molten Pool during Laser Remelting

采用类金属透明模型合金SCN-Eth合金,在自主搭建的激光熔池凝固过程宏微观实时观察平台上,研究了激光重熔过程中熔池宏微观形态演化规律。研究发现,随着激光束扫描的进行,熔池及其热影响区的宏观形态都先从圆形变为椭圆形,最后演化为尾部呈"V"形的泪滴状。随着激光功率的增加,稳态熔池长度L、宽度W、尾部夹角α均增加;随着扫描速度的增大,稳态熔池长度L、宽度W、夹角α均减小;熔池长宽比随功率的增加而增大,随扫描速度的增加先增大后减小。从熔池中部到熔池尾部液固界面形貌依次呈平面→胞晶→枝晶演化,胞晶和枝晶一次间距不同,浅胞间距约为28μm,深胞间距约为42μm,枝晶间距约为65μm,胞枝晶一次间距沿固液界面增大。

In this paper,a transparent model alloy SCN-Eth alloys,in self-built visualization metal-analog laser molten pool solidification process experiment platform,are used to research the evolution of the laser molten pool macroscopic morphology and microstructure of the molten pool solidification.The main conclusions are as follows：in the unsteady evolution,both molten pool and its heat affect zone geometry from circular to elliptical,finally evolved into the tail with ＂ V＂-shaped teardropshaped.With the increase of the laser power,steady pool length L,width W,the angleαwere increased;with increasing scan speed,the steady pool length L,width W,the angleαwere less small;the length-width ratio of the molten pool increases with the increasing laser power,while,with the increasing scanning speed,the length-width ratio increases first and then decreases.From the middle of the pool to the tail of the pool,we can see the evolution of the interface morphology：plane crystal→cell→dendrites,the primary dendrite spacing of the cells and dendrites are different,the primary dendrite spacing of shallow cells about 28μm,deep cell is about 42μm,while the primary dendrite spacing of dendrites is about 65μm,the primary dendrite spacing of the cells and dendrites are increased.