Ti6Al4V合金毫秒激光打孔重铸层的形成机制
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摘要
Ti6Al4V合金在毫秒激光打孔过程中,沿孔壁会形成严重影响成品性能的重铸层。考虑熔体受到的热学和力学等方面的影响,基于修改的流体力学方程和改进的水平集法,建立了激光打孔的固/液/气三相二维数值计算模型,在单脉冲能量为3J的条件下,对不同脉宽参数的激光打孔进行数值研究。运用后处理技术提取了打孔过程中重铸层的温度场、流场和厚度分布情况。结果表明,蒸发和喷溅是熔体排除的主要方式,重铸层是在热-力耦合作用下形成的。重铸层的厚度随激光脉宽的增大而增加,并呈现从孔口到孔底逐渐变薄的特征。
During the process of millisecond laser drilling of Ti6Al4 V alloys,the recast layer forms along hole walls,which is a serious detriment to hole quality.In consideration of the thermal and mechanical parameters influencing melt and based on the modified equations of fluid mechanics and improved Level-Set method,a solid/liquid/gas three-phase two dimensional numerical model is constructed used for laser drilling.The numerical investigation of laser drilling with different pulse widths and with single pulse energy of 3Jis conducted.The temperature field,flow field,and thickness distribution of recast layer during the drilling process are obtained by using the post-processing technology.The results indicate that molten liquid is discharged mainly by means of evaporation and ejection and the recast layer is formed under the coupling effect of heat and force.The recast layer thickness increases with the increment of laser pulse width,which possesses a characteristic of recast layer becoming thin slowly from top hole to bottom hole.
During the process of millisecond laser drilling of Ti6Al4 V alloys,the recast layer forms along hole walls,which is a serious detriment to hole quality.In consideration of the thermal and mechanical parameters influencing melt and based on the modified equations of fluid mechanics and improved Level-Set method,a solid/liquid/gas three-phase two dimensional numerical model is constructed used for laser drilling.The numerical investigation of laser drilling with different pulse widths and with single pulse energy of 3Jis conducted.The temperature field,flow field,and thickness distribution of recast layer during the drilling process are obtained by using the post-processing technology.The results indicate that molten liquid is discharged mainly by means of evaporation and ejection and the recast layer is formed under the coupling effect of heat and force.The recast layer thickness increases with the increment of laser pulse width,which possesses a characteristic of recast layer becoming thin slowly from top hole to bottom hole.
引文
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[20]Pang S Y,Hirano K,Fabbro R,et al.Explanation of penetration depth variation during laser welding under variable ambient pressure[J].Journal of Laser Applications,2015,27(2):022007.
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[22]Courtois M,Carin M,Masson P L,et al.A new approach to compute multi-reflections of laser beam in a keyhole for heat transfer and fluid flow modelling in laser welding[J].Journal of Physics D-Applied Physics,2013,46(50):505305.
[23]Riveiro A,Quintero F,Lusquios F,et al.Study of melt flow dynamics and influence on quality for CO2laser fusion cutting[J].Journal of Physics D-Applied Physics,2011,44(13):135501.
[24]Wei P S,Wu J H,Chao T C,et al.Keyhole collapse during high intensity beam drilling[J].International Journal of Heat and Mass Transfer,2014,79:300-308.
[25]Bandyopadhyay S,Sundar J K S,Sundararajan G,et al.Geometrical features and metallurgical characteristics of Nd∶YAG laser drilled holes in thick IN718and Ti-6Al-4Vsheets[J].Journal of Materials Processing Technology,2002,127(1):83-95.
[2]Zhao Shiqiang,Li Ling.Numerical investigation of phase change during thermal ablation of gold films induced by femtosecond laser[J].Acta Optica Sinica,2015,35(12):1214001.赵士强,李凌.飞秒脉冲激光烧蚀金膜的相变传热研究[J].光学学报,2015,35(12):1214001.
[3]Leigh S,Sezer K,Li L,et al.Statistical analysis of recast formation in laser drilled acute blind holes in CMSX-4nickel superalloy[J].International Journal of Advanced Manufacturing Technology,2009,43(11-12):1094-1105.
[4]Zhang T Z,Jia Z C,Cui H C,et al.Analysis of melt ejection during long pulsed laser drilling[J].Chinese Physics B,2016,25(5):054206.
[5]Voisey K T,Klocker T,Clyne T W.Measurement of melt ejection velocities during laser drilling of steel,using a novel droplet stream interception technique[J].Acta Materialia,2002,50(17):4219-4230.
[6]Low D K Y,Li L,Byrd P J.Spatter prevention during the laser drilling of selected aerospace materials[J].Journal of Materials Processing Technology,2003,139(1-3):71-76.
[7]Duan W Q,Wang K D,Dong X,et al.Experimental characterizations of burr deposition in Nd∶YAG laser drilling:Aparametric study[J].International Journal of Advanced Manufacturing Technology,2015,76(9-12):1529-1542.
[8]Yilbas B S,Karatas C,Uslan,et al.CO2laser gas assisted nitriding of Ti-6Al-4Valloy[J].Applied Surface Science,2006,252(24):8557-8564.
[9]Yilbas B S,Sami M.Liquid ejection and possible nucleate boiling mechanisms in relation to the laser drilling process[J].Journal of Physics D-Applied Physics,1997,30(14):1996-2005.
[10]Yang C J,Mei X S,Wang W J,et al.Recast layer removal using ultrafast laser in titanium alloy[J].International Journal of Advanced Manufacturing Technology,2013,68(9-12):2321-2327.
[11]Duan W Q,Dong X,Wang K D,et al.Effect of temporally modulated pulse on reducing recast layer in laser drilling[J].The International Journal of Advacned Manufacturing Technology,2016,87(5):1641-1652.
[12]Bandyopadhyay S,Gokhale H,Sundar J K S,et al.A statistical approach to determine process parameter impact in Nd∶YAG laser drilling of IN718and Ti-6Al-4Vsheets[J].Optics and Lasers in Engineering,2005,43(2):163-182.
[13]Song Linsen,Shi Guoquan,Li Zhanguo.Simulation of laser drilling temperature field by using ANSYS[J].Acta Armamentarii,2006,27(5):879-882.宋林森,史国权,李占国.利用ANSYS进行激光打孔温度场仿真[J].兵工学报,2006,27(5):879-882.
[14]Chu Qingchen,Yu Gang,Lu Guoquan,et al.Two-dimensional numerical investigation for the effects of laser process parameters on hole type during laser drilling[J].Chinese J Lasers,2011,38(6):0603001.褚庆臣,虞钢,卢国权,等.激光打孔工艺参数对孔型影响的二维数值模拟研究[J].中国激光,2011,38(6):0603001.
[15]Zhang Y W,Faghri A.Vaporization,melting and heat conduction in the laser drilling process[J].International Journal of Heat and Mass Transfer,1999,42(10):1775-1790.
[16]Hirano K,Fabbro R.Experimental investigation of hydrodynamics of melt layer during laser cutting of steel[J].Journal of Physics D-Applied Physics,2011,44(10):105502.
[17]Ki H,Mohanty P S,Mazumder J.Modelling of high-density laser-material interaction using fast level set method[J].Journal of Physics D-Applied Physics,2001,34(3):364-372.
[18]Otto A,Koch H,Leitz K H,et al.Numerical simulations-A versatile approach for better understanding dynamics in laser material processing[C].Physics Procedia,2011,12:11-20.
[19]Pang S Y,Chen X,Zhou J X,et al.3Dtransient multiphase model for keyhole,vapor plume,and weld pool dynamics in laser welding including the ambient pressure effect[J].Optics and Lasers in Engineering,2015,74:47-58.
[20]Pang S Y,Hirano K,Fabbro R,et al.Explanation of penetration depth variation during laser welding under variable ambient pressure[J].Journal of Laser Applications,2015,27(2):022007.
[21]Fabbro R,Hirano K,Pang S Y.Analysis of the physical processes occurring during deep penetration laser welding under reduced pressure[J].Journal of Laser Applications,2016,28(2):022427.
[22]Courtois M,Carin M,Masson P L,et al.A new approach to compute multi-reflections of laser beam in a keyhole for heat transfer and fluid flow modelling in laser welding[J].Journal of Physics D-Applied Physics,2013,46(50):505305.
[23]Riveiro A,Quintero F,Lusquios F,et al.Study of melt flow dynamics and influence on quality for CO2laser fusion cutting[J].Journal of Physics D-Applied Physics,2011,44(13):135501.
[24]Wei P S,Wu J H,Chao T C,et al.Keyhole collapse during high intensity beam drilling[J].International Journal of Heat and Mass Transfer,2014,79:300-308.
[25]Bandyopadhyay S,Sundar J K S,Sundararajan G,et al.Geometrical features and metallurgical characteristics of Nd∶YAG laser drilled holes in thick IN718and Ti-6Al-4Vsheets[J].Journal of Materials Processing Technology,2002,127(1):83-95.