摘要
通过有限元方法对介观尺度下SLM过程中316L熔池匙孔演变及热力学行为和由此产生的表面形貌进行了分析,并结合试验进行了验证。发现匙孔熔池的自由表面被蒸发金属的高温气体所覆盖,导致反冲压力的产生并伴随自由表面的变形。在成形过程的初始阶段,熔池边缘金属向内的对流阻止了熔池的扩展,而随后形成的向外对流促进了熔体流动,保证了凝固后相邻熔池的搭接。金属汽化产生向表面的后坐压力,在熔池内引起湍流飞溅,这些飞溅被移到激光路径外侧并凝固成粘结的驼峰结构,无法在下一层成形时熔化。随着层数的增加,熔池自由表面出现凹型轮廓和材料粘结。采用纳米压痕实验对成形后熔池的3个位置进行了局域弹塑性力学性能研究,发现熔池的搭接区域压痕硬度和弹性模量最高,分别为4.08 GPa和211.45 GPa。
The keyhole evolution,thermodynamic behavior and surface morphology of 316L molten pool during SLM at mesoscopic scale were analyzed by finite element method.And it was verified by test.It is found that the free surface of the keyhole molten pool is covered by the high-temperature gas of evaporated metal,resulting in the generation of recoil pressure and the deformation of the free surface.In the initial stage of the forming process,the inward convection of the metal at edge of molten pool prevents the expansion of the molten pool,while the subsequent outward convection promotes the melt flow and ensures the overlap of adjacent molten pools after solidification.The recoil pressure towards the surface due to metal vaporization causes a turbulent splashing in the molten pool.These sputters are moved to the outside of the laser path and solidified into a bonded hump structure that could not melt during the formation of next layer.As the number of layers increases,the free surface of the melt pool has concave profiles and material bonding.The local elastic-plastic mechanical properties of three positions of the molten pool were studied by nano indentation experiment.It is found that the indentation hardness and elastic modulus of the lap area in the molten pool are the highest,which are 4.08 GPa and 211.45 GPa,respectively.
作者
汤晓刚
陈伟
刘俊悦
陈磊
TANG Xiaogang;CHEN Wei;LIU Junyue;CHEN Lei(Anhui Huadian Engineering Consultating&Design Co.,Ltd.,Hefei 230022,China;Hefei Innovation Research Institute,Beihang University,Hefei 230012,China)
出处
《热加工工艺》
北大核心
2023年第21期38-43,共6页
Hot Working Technology
作者简介
汤晓刚(1984-),男,安徽合肥人,硕士研究生,研究方向:输变电工程与表面工程,E-mail:tangxiaogang126@126.com;通讯作者:陈磊(1986-),男,安徽合肥人,博士,研究方向为结构力学,E-mail:chenlei2019@buaa.edu.cn。
