激光重熔熔池凝固组织的实时观察研究  

REAL-TIME OBSERVATION OF SOLIDIFICATION MICROSTRUCTURE IN LASER REMELTING POOL

作　　者：王理林[1] 林鑫[1] 王永辉[1] 宇红雷[1] 黄卫东[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,西安710072

出　　处：《金属学报》2015年第4期492-498,共7页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目51271213和51323008;国家重点基础研究发展计划项目2011CB610402;中国博士后科学基金项目2013M542384;高等学校博士学科点专项科研基金项目20116102110016资助~~

摘　　要：采用透明模型合金丁二腈-2.0%(质量分数)乙醇(SCN-2.0%Eth),实时观察了在单晶基材(001)晶面上进行激光重熔时,扫描方向偏离基材[100]晶向不同角度时熔池内枝晶生长的演化过程.研究发现,当沿平行[100]晶向的方向进行扫描时,熔池最后演变为[010]枝晶列和[01ˉ0]枝晶列平行对称生长;当扫描方向与[100]晶向的夹角为20°时,整个熔池呈现不对称振荡生长模式,即一侧一直呈[01ˉ0]枝晶列生长,另一侧呈[100]枝晶列和[010]枝晶列相互竞争交替生长;当扫描方向与[100]晶向的夹角达45°时,熔池一直呈现为[100]枝晶列和[01ˉ0]枝晶列相互垂直生长.根据枝晶择优生长准则,建立了一个描述熔池内枝晶生长行为的模型,很好地解释了实验结果.结果表明,熔池内凝固组织受熔池形态和基材晶体取向共同影响.ABSTRACT The final quality of parts fabricated by high energy beam （laser, electron beam and arc） processing technology is determined by solidification microstructure formation in the molten pool, which attracts lot of atten- tion of researches. However, real-time observation of solidification microstructure formation in the molten metal pool is very difficult because of its high temperature, rapid solidification and opacity. In this work, using a transpar- ent model alloy of succinonitrile-2.0% （mass fraction） ethanol （SCN-2.0%Eth）, the solidification microstructure evolution in the molten pool during laser surface remelting （001） crystal plane of a single-crystal substrate was real- time observed as the laser scanning direction deviated different angles from [100] crystal orientation of the sub- strate. It was found that [010] and [0i0] dendritic columns grow symmetrically in the molten pool when the scan- ning direction parallels to the [100] crystal direction. Dendritic columns grow asymmetrically in the molten pool when the scanning direction deviates an angle of 20~ from the [100] crystal orientation. Specifically, [010] dendrit- ic columns always grow at one side of the molten pool while [100] and [010] dendritic columns compete to grow alternately at the other side. [100] and [010] dendritic columns grow perpendicular to each other in the molten pool when the scanning direction deviates an angle of 45° from the [ 100] crystal orientation. According to the pref-erential growth criterion of dendrite, a model describing the dendritic growth behavior in laser remelting pool was established. It can explain the experimental results well. The results showed that the solidification microstructure formation in laser remelting pool is influenced by both pool morphology and crystal orientation of the substrate.

关 键 词：激光重熔 单晶 熔池 枝晶 透明模型合金 实时观察 

分 类 号：TG24[金属学及工艺—铸造]